429 articles found
Cama-Moncunill, R. ; Cama-Moncunill, X. ; Casado-Gavalda, M. P. ; Cullen, P. J. ; Dixit, Y. ; Sullivan, C.
LIBS; Gluten free flour; Ash content; Mineral content;TARTARY BUCKWHEAT; RICE; SAMPLES; CHEMOMETRICS; ADULTERATION; ELEMENTS; MILK; MEAT
Gluten free (GF) diets are prone to mineral deficiency, thus effective monitoring of the elemental composition of GF products is important to ensure a balanced micronutrient diet. The objective of this study was to test the potential of laser-induced breakdown spectroscopy (LIBS) analysis combined with chemometrics for at-line monitoring of ash, potassium and magnesium content of GF flours: tapioca, potato, maize, buckwheat, brown rice and a GF flour mixture. Concentrations of ash, potassium and magnesium were determined with reference methods and LIBS. PCA analysis was performed and presented the potential for discrimination of the six GF flours. For the quantification analysis PLSR models were developed; R(2)cal were 0.99 for magnesium and potassium and 0.97 for ash. The study revealed that LIBS combined with chemometrics is a convenient method to quantify concentrations of ash, potassium and magnesium and present the potential to classify different types of flours.
Laser-induced breakdown spectroscopy; Stand-off analysis; Solid aerosol detection; Steelshop atmosphere; Continuous casting line; Sampling rate;INDUCED BREAKDOWN SPECTROSCOPY; AEROSOL-PARTICLES; INTEGRATED IRON; AIR; TEMPERATURE; EMISSIONS; OXIDATION; ALUMINUM; SURFACES; ALLOYS
The analytical possibilities of laser induced breakdown spectroscopy (LIBS) to carry out in-situ and real-time detection and compositional characterization of aerosols in the atmosphere of a steelmaking factory, have been evaluated. To this aim, a compact and versatile dual-pulse LIBS analyzer, able to sample at distances up to eight meters, has been designed to work in these hostile industrial environments. Due to the discrete nature of the particulate matter, the particle sampling rate was less than 2.5% and 6% for single-and double-pulse regimes, respectively. An efficient statistical procedure, based on the calculation of standard deviations, is used to qualitatively characterize the elemental composition of the aerosol. Then, a conditional analysis based on the limit of detection, is employed to assess the elemental sampling rate. This experimental methodology has been used to evaluate the influence on the aerosol formed of the oxycutting process in a continuous casting machine producing steel slabs, revealing a strong presence of elements derived from the casting powder used in the production. Moreover, chromium, present in the steel cast, is detected in aerosol suspension in the steel shop. An increase in the concentration of particulate matter was expected when oxycutting was on. Single-pulse and dualpulse excitation modes are also evaluated.
Titanium dioxide; Laser induced breakdown spectroscopy; White chickpea; Partial least square analysis;INDUCED BREAKDOWN SPECTROSCOPY; PLASMA-MASS SPECTROMETRY; EMISSION-SPECTROMETRY; FOOD; NANOPARTICLES; PARTICLES; PRODUCTS; LIBS; CELLS
Titanium dioxide (TiO2) is a widely used additive in foods. However, in the scientific community there is an ongoing debate on health concerns about TiO2. The main goal of this study is to determine TiO2 content by using laser induced breakdown spectroscopy (LIBS). To this end, different amounts of TiO2 was added to white chickpeas and analyzed by using LIBS. Calibration curve was obtained by following Ti emissions at 390.11 nm for univariate calibration, and partial least square (PLS) calibration curve was obtained by evaluating the whole spectra. The results showed that Ti calibration curve at 390.11 nm provides successful determination of Ti level with 0.985 of R-2 and 33.9 ppm of limit of detection (LOD) value, while PLS has 0.989 of R-2 and 60.9 ppm of LOD. Furthermore, commercial white chickpea samples were used to validate the method, and validation R-2 for simple calibration and PLS were calculated as 0.989 and 0.951, respectively.
Zhundong coal; Sodium; Alkali metal; Sorbent additives; LIBS;INDUCED BREAKDOWN SPECTROSCOPY; FIXED-BED REACTOR; ATOMIC SODIUM; BROWN-COAL; ALKALI REMOVAL; COMBUSTION; PYROLYSIS; SORBENTS; GASIFICATION; TEMPERATURE
The retention performance of 5 different sorbent additives, including 2 pure additives, i.e., silica and alumina, and 3 typical natural mineral additives, i.e., kaolin, mica and pyrophyllite, on the release of sodium during the combustion of Zhundong coal is investigated via a combination of online multi-point Laser-Induced Breakdown Spectroscopy (LIBS) technique and offline measurements including inductively coupled plasma atomic emission spectrometer (ICP-AES), X-ray diffraction, and ash fusion temperatures (AFTs). The online and offline measurement results for the sodium release of Zhundong coal/additives mixtures are compared and verified with each other. Ternary phase diagram simulations are performed to further substantiate the impact of different additives on liquidus temperatures of Zhundong coal ash. All the five sorbent additives show a significant sodium retention effect, while alumina and kaolin are better additives considering the effects on AFTs.
A spectrometer based on pulsed nanosecond laser-induced breakdown spectroscopy (LIBS) was employed for the quantitative determination of heavy and essential metals in salts from various sources available in Pakistan. Six salt samples were collected from sea salt and rock salt. Toxic metals (Cu, Cd, and Ni) and other microessentials (Fe, Ca, Co, Mg, Mn, S, and Zn) were investigated from the recorded spectra. The detection system was calibrated using a parametric dependence study. The quantitative analyses were accomplished under the assumption of local thermodynamic equilibrium and optically thin plasma. The results by the LIBS technique were in agreement with the outcomes of the same samples studied using a more standard approach like inductively coupled plasma-atomic emission spectroscopy (ICP-AES). When the concentrations of heavy and essential metals were calculated using a calibration-free LIBS method that does not need a standard salt specimen and dilution, both LIBS and ICP-AES were also in good agreement. The limit of detection of the experimental set up was determined for the observed heavy metals in the studied samples. (c) 2018 Optical Society of America
Artificial neural network; Chinese herbal medicine; laser-induced breakdown spectroscopy (LIBS); principal component analysis;SOLID-PHASE EXTRACTION; CAPILLARY-ELECTROPHORESIS; INFRARED-SPECTROSCOPY; QUANTITATIVE-ANALYSIS; DISCRIMINANT-ANALYSIS; RAPID ANALYSIS; TEA SAMPLES; TLC-SERS; LIBS; CHEMOMETRICS
Chinese herbal medicine has attracted increasing attention because of the unique and significant efficacy in various diseases. In this paper, three types of Chinese herbal medicine, the roots of Angelica pubescens, Codonopsis pilosula, and Ligusticum wallichii with different places of origin or parts, are analyzed and identified using laser-induced breakdown spectroscopy (LIBS) combined with principal component analysis (PCA) and artificial neural network (ANN). The study of the roots of A. pubescens was performed. The score matrix is obtained by principal component analysis, and the backpropagation artificial neural network (BP-ANN) model is established to identify the origin of the medicine based on LIBS spectroscopy of the roots of A. pubescens with three places of origin. The results show that the average classification accuracy is 99.89%, which exhibits better prediction of classification than linear discriminant analysis or support vector machine learning methods. To verify the effectiveness of PCA combined with the BP-ANN model, this method is used to identify the origin of C. pilosula. Meanwhile, the root and stem of L. wallichii are analyzed by the same method to distinguish the medicinal materials accurately. The recognition rate of C. pilosula is 95.83%, and that of L. wallichii is 99.85%. The results present that LIBS combined with PCA and BP-ANN is a useful tool for identification of Chinese herbal medicine and is expected to achieve automatic real-time, fast, and powerful measurements.
laser induced breakdown spectroscopy; EAST tokamak; temporal and spatial dynamics;INDUCED BREAKDOWN SPECTROSCOPY; TUNGSTEN PLASMA; MAGNETIC-FIELD; DIAGNOSTICS; DEPOSITION
Laser-induced breakdown spectroscopy (LIBS) has been developed to in situ diagnose the chemical compositions of the first wall in the EAST tokamak. However, the dynamics of optical emission of the key plasma-facing materials, such as tungsten, molybdenum and graphite have not been investigated in a laser produced plasma (LPP) under vacuum. In this work, the temporal and spatial dynamics of optical emission were investigated using the spectrometer with ICCD. Plasma was produced by an Nd:YAG laser (1064 nm) with pulse duration of 6 ns. The results showed that the typical lifetime of LPP is less than 1.4 mu s, and the lifetime of ions is shorter than atoms at similar to 10(-6) mbar. Temporal features of optical emission showed that the optimized delay times for collecting spectra are from 100 to 400 ns which depended on the corresponding species. For spatial distribution, the maximum LIBS spectral intensity in plasma plume is obtained in the region from 1.5 to 3.0 mm above the sample surface. Moreover, the plasma expansion velocity involving the different species in a multicomponent system was measured for obtaining the proper timing (gate delay time and gate width) of the maximum emission intensity and for understanding the plasma expansion mechanism. The order of expansion velocities for various species is V-C+ > V-H > V-Si+ > V-Li > V-Mo > V-W. These results could be attributed to the plasma sheath acceleration and mass effect. In addition, an optimum signal-to-background ratio was investigated by varying both delay time and detecting position.
INDUCTIVELY-COUPLED PLASMA; X-RAY-FLUORESCENCE; SOLID-PHASE EXTRACTION; INDUCED BREAKDOWNSPECTROSCOPY; MC-ICP-MS; RARE-EARTH-ELEMENTS; OPTICAL-EMISSION SPECTROMETRY; LIQUID-LIQUID MICROEXTRACTION; ISOTOPE RATIO MEASUREMENTS; IONIZATION MASS-SPECTROMETRY
This is the 33th annual review of the application of atomic spectrometry to the chemical analysis of environmental samples. This update refers to papers published approximately between August 2016 and June 2017 and continues the series of Atomic Spectrometry Updates (ASUs) in environmental analysis(1) that should be read in conjunction with other related ASUs in the series, namely: clinical and biological materials, foods and beverages; 2 advances in atomic spectrometry and related techniques; 3 elemental speciation; 4 X-ray spectrometry; 5 and metals, chemicals and functional materials. 6 In the field of air analysis, highlights within this review period included the fabrication of new air samplers using 3D printer technology, development of a portable aerosol concentrator unit based upon electrostatic precipitation and instrumental developments such as a prototype portable spark emission spectrometer to quantify metal particles in workplace air. The advent of ICP-MS/MS systems has enabled analysts to develop improved methods for the determination of PGEs and radioactive elements present in airborne particles. With such instruments, the capacity to eliminate or minimise many isobaric interferences now enables analysts to forego the use of many onerous sample cleanup procedures. Improvements in the capabilities of aerosol mass spectrometers were noted as were developments in other complimentary measurement techniques such as Raman. In the arena of water analysis there are growing concerns regarding engineered NPs e.g. Ag NPs, entering water courses resulting in the development and optimisation of new methods based upon FFF and sp-ICP-MS techniques to measure such inputs. Similar concerns exist for MRI contrasting agents e.g. Gd-based compounds and here improved methodologies that involve the use of sample preconcentration using chelating columns and ICP-MS analysis have been proposed. In the field of plant and soil analysis, similar to developments in the water sector, there has been increased interest in the measurement of NPs. Many comparisons of sample digestion or extraction methods have been reported but a key issue rarely addressed is transferability, i.e. whether methods preferred by one group of researchers using particular apparatus are also optimal in a different laboratory using different apparatus. New sample preconcentration methods continued to appear although-as in previous years - the CRMs selected for method validation often failed to reflect the nature of the intended sample(s). A noteworthy advance is the use of HR-CS-ETMAS for elemental analysis. Developments in LIBS included greater use of TEA CO2 lasers in place of Nd:YAG lasers and increased use of stand-off measurement. The past year has also seen a rise in proximal sensing using LIBS and pXRFS. In the field of geological analysis, the quest continues for well-characterised matrix-matched materials suitable for the calibration of elemental and, particularly, isotopic measurements by microanalytical techniques. Increasing interest in stable isotope analysis by SIMS is reflected by the number of matrix-matched RMs developed specifically for this technique. Much work continues on ways of improving isotope ratio measurements by ICP-MS and TIMS for a wide range of different isotope systems relevant to geochemical studies. High spatial resolution analysis by LIBS, LA-ICP-MS and SIMS to obtain data on chemical and isotopic variations in minerals and biogenic materials in two and three dimensions are the foundation for many new insights in geoscientific research. In XRFS and LIBS, the advantages and limitations of portable instrumentation continue to be major focus of activity.
INDUCED BREAKDOWN SPECTROSCOPY; LEVITATED DROPLETS; MASS-SPECTROMETRY; AIR SPARK; ELEMENTS; ZINC; LEAD
Optical elemental analysis in the gas phase typically relies on electrically driven plasmas. As an alternative approach, laser-induced plasmas (LIPs) have been suggested but have so far been only scarcely used. Here, a novel signal enhancement strategy for laser-based airborne plasma optical emission spectroscopyfor gas phase analytics is presented. In contrast to an electrically driven plasma, in the laser-induced analogue dynamic matter transport equilibrium builds up. The latter results in a rarefied density regime in the plasma core itself, surrounded by an area of compressed matter. The central rarefaction leads to a decrease in plasma intensity and analyte number density, both of which are detrimental for analytical purposes. Since the repetitive ignition of LIPs is a transient process, a restoration of the former gaseous medium by other dynamically equilibrated diffusion processes would be favourable. The presented combination of an airborne LIP and an ultrasonic acoustic resonator yields a fourfold signal enhancement while the background contribution of ubiquitous air is at the same time effectively suppressed. Since the entire enhancement effect occurs without contact, no additional sources for abrasive sample contamination are introduced.
LIBS; Karats of gold; Elemental composition; Plasma parameters; LA-TOF-mass spectrometry;ELEMENTAL ANALYSIS; OSCILLATOR-STRENGTHS; INDUCED PLASMA; ALLOYS; TRANSITIONS; LIFETIMES; LITHIUM; SAMPLES; LINES
Laser induced breakdown spectroscopy (LIBS) coupled with a laser ablation time of flight mass spectrometer (LA-TOF-MS) has been developed for discrimination/analysis of the precious gold alloys cartage. Five gold alloys of Karats 18K, 19K, 20K, 22K and 24K having certified composition of gold as 75, 79, 85, 93 and 99.99% were tested and their precise elemental compositions were determined using the laser produced plasma technique. The plasma was generated by focusing beam of a Nd:YAG laser on the target in air and its time integrated emission spectra were registered in the range 250-870 nm. The calibration free LIBS technique (CF-LIBS) was used for the quantitative determination of the constituent elements present in different Karats of gold. Elemental compositions of these gold alloys were also determined using a Laser Ablation time of flight mass spectrometer (LA-TOF-MS). The LIBS limit of detection was calculated from the calibration curves for copper, silver and gold. Results of CF-LIBS and LA-TOF-MS are in excellent agreement with the certified values. It is demonstrated that LIBS coupled with LA-TOF-MS is an efficient technique that can be used to analyze any precious alloys in a fraction of a second.
Raw materials; Particles; Raman; Infrared; Spectroscopy; Laser-induced breakdown spectroscopy (LIBS);
Raw materials need to be of a certain quality with respect to physical and chemical composition. They also need to have no contaminants in the form of particles because these could get into the product or indicate the raw materials are not pure enough to make a good quality product. When particles are found, it is important to identify their chemical and elemental composition to correct any process errors that can cause them and to have acceptable quality of the final product. Sources of materials can be the environment, process equipment and processing, and packaging. Microscope versions of Raman spectroscopy, laser-induced breakdown spectroscopy (LIBS), and IR spectroscopy are excellent tools for identifying particles in materials because they are fast and accurate techniques needing minimal sample preparation that can provide chemical composition as well as images that can be used for identification. The micro analysis capabilities allow for easy analysis of different portions of samples so that multiple components can be identified and sample preparation can be reduced or eliminated. The complementarity of the techniques provides the advantage of identifying various chemical components, as well as elemental and image analyses. The sources of materials were seen to be the environment, process equipment and processing, and packaging.
Laser-induced breakdown spectroscopy; LIBS; multivariate analysis; univariate analysis; milk; protein; principal component analysis; PCA; partial least squares regression; PLSR;CHEMOMETRICS; SPECTRA; FLOUR
Laser-induced breakdown spectroscopy (LIBS) technique was used to compare various types of commercial milk products. Laser-induced breakdown spectroscopy spectra were investigated for the determination of the elemental composition of soy and rice milk powder, dairy milk, and lactose-free dairy milk. The analysis was performed using radiative transitions. Atomic emissions from Ca, K, Na, and Mg lines observed in LIBS spectra of dairy milk were compared. In addition, proteins and fat level in milks can be determined using molecular emissions such as CN bands. Ca concentrations were calculated to be 2.165 +/- 0.203g/L in 1% of dairy milk fat samples and 2.809 +/- 0.172g/L in 2% of dairy milk fat samples using the standard addition method (SAM) with LIBS spectra. Univariate and multivariate statistical analysis methods showed that the contents of major mineral elements were higher in lactose-free dairy milk than those in dairy milk. The principal component analysis (PCA) method was used to discriminate four milk samples depending on their mineral elements concentration. In addition, proteins and fat level in dairy milks were determined using molecular emissions such as CN band. We applied partial least squares regression (PLSR) and simple linear regression (SLR) models to predict levels of milk fat in dairy milk samples. The PLSR model was successfully used to predict levels of milk fat in dairy milk sample with the relative accuracy (RA%) less than 6.62% using CN (0,0) band.
Rare earth elements; REE; geological samples; laser-induced breakdown spectroscopy; LIBS;GLASSES; COAL
Laser-induced breakdown spectroscopy (LIBS) was used to detect rare earth elements (REEs) in natural geological samples. Low and high intensity emission lines of Ce, La, Nd, Y, Pr, Sm, Eu, Gd, and Dy were identified in the spectra recorded from the samples to claim the presence of these REEs. Multivariate analysis was executed by developing partial least squares regression (PLS-R) models for the quantification of Ce, La, and Nd. Analysis of unknown samples indicated that the prediction results of these samples were found comparable to those obtained by inductively coupled plasma mass spectrometry analysis. Data support that LIBS has potential to quantify REEs in geological minerals/ores.
Calibration-free laser-induced breakdown spectroscopy; CF-LIBS; self-absorption correction; internal reference line auto-selection; plasma temperature estimation;ALUMINUM EMISSION-LINES; SELF-ABSORPTION; NORMALIZATION; REGRESSION; ALGORITHM; ACCURACY; AEROSOLS; RATIOS; ALLOYS; MODEL
The quantitative analysis accuracy of calibration-free laser-induced breakdown spectroscopy (CF-LIBS) is severely affected by the self-absorption effect and estimation of plasma temperature. Herein, a CF-LIBS quantitative analysis method based on the auto-selection of internal reference line and the optimized estimation of plasma temperature is proposed. The internal reference line of each species is automatically selected from analytical lines by a programmable procedure through easily accessible parameters. Furthermore, the self-absorption effect of the internal reference line is considered during the correction procedure. To improve the analysis accuracy of CF-LIBS, the particle swarm optimization (PSO) algorithm is introduced to estimate the plasma temperature based on the calculation results from the Boltzmann plot. Thereafter, the species concentrations of a sample can be calculated according to the classical CF-LIBS method. A total of 15 certified alloy steel standard samples of known compositions and elemental weight percentages were used in the experiment. Using the proposed method, the average relative errors of Cr, Ni, and Fe calculated concentrations were 4.40%, 6.81%, and 2.29%, respectively. The quantitative results demonstrated an improvement compared with the classical CF-LIBS method and the promising potential of in situ and real-time application.
Bukin, V. V. ; Fedorov, A. N. ; Grishin, M. Y. ; Oshurko, V. B. ; Pershin, S. M. ; Sdvizhenskii, P. A. ; Shchegolikhin, A. N.
Laser induced breakdown spectroscopy; LIBS; Raman scattering; Double pulse; Quantitative analysis;QUANTITATIVE-ANALYSIS; LIBS; SPECTROMETER; MICROSCOPY; MINERALS; PIGMENTS; PLATFORM; ASPIRIN; SYSTEM; CRATER
A new approach combining Raman spectrometry and laser induced breakdown spectrometry (LIBS) within a single laser event was suggested. A pulsed solid state Nd:YAG laser running in double pulse mode (two frequency-doubled sequential nanosecond laser pulses with dozens microseconds delay) was used to combine two spectrometry methods within a single instrument (Raman/LIBS spectrometer). First, a low-energy laser pulse (power density far below ablation threshold) was used for Raman measurements while a second powerful laser pulse created the plasma suitable for LIBS analysis. A short time delay between two successive pulses allows measuring LIBS and Raman spectra at different moments but within a single laser flash-lamp pumping. Principal advantages of the developed instrument include high quality Raman/LIBS spectra acquisition (due to optimal gating for Raman/LIBS independently) and absence of target thermal alteration during Raman measurements. A series of high quality Raman and LIBS spectra were acquired for inorganic salts (gypsum, anhydrite) as well as for pharmaceutical samples (acetylsalicylic acid). To the best of our knowledge, the quantitative analysis feasibility by combined Raman/LIBS instrument was demonstrated for the first time by calibration curves construction for acetylsalicylic acid (Raman) and copper (LIBS) in gypsum matrix. Combining ablation pulses and Raman measurements (LIBS/Raman measurements) within a single instrument makes it an efficient tool for identification of samples hidden by non-transparent covering or performing depth profiling analysis including remote sensing.
CF-LIBS; internal reference self-absorption correction (IRSAC); brass; quantitative analysis; plasma parameters; energy dispersive x-ray spectroscopy (EDX); laser ablation time-of-flight mass spectrometry (LA-TOF-MS);INDUCED BREAKDOWN SPECTROSCOPY; CALIBRATION-FREE; ELEMENTAL ANALYSIS; PLASMA TEMPERATURE; PARAMETERS; ACCURACY
We present a quantitative analysis of a brass alloy using laser induced breakdown spectroscopy, energy dispersive x-ray spectroscopy (EDX) and laserablation time-of-flight mass spectrometry (LA-TOF-MS). The emission lines of copper (Cu I) and zinc (Zn I), and the constituent elements of the brass alloy were used to calculate the plasma parameters. The plasma temperature was calculated from the Boltzmann plot as (10 000 +/- 1000) K and the electron number density was determined as (2.0 +/- 0.5) x 10(17) cm(-3) from the Stark-broadened Cu I line as well as using the Saha-Boltzmann equation. The elemental composition was deduced using these techniques: the Boltzmann plot method (70% Cu and 30% Zn), internal reference self-absorption correction (63.36% Cu and 36.64% Zn), EDX (61.75% Cu and 38.25% Zn), and LA-TOF (62% Cu and 38% Zn), whereas, the certified composition is (62% Cu and 38% Zn). It was observed that the internal reference self-absorption correction method yields analytical results comparable to that of EDX and LA-TOF-MS.
Kumar, G. A. ; Nayak, R. ; Patil, A. ; Shameem, K. M. M. ; Tamboli, M. M. ; Unnikrishnan, V. K.
rare earth elements; absorption; fluorescence; laser-induced breakdown spectroscopy (LIBS);INDUCED BREAKDOWN SPECTROSCOPY; OPTICAL-PROPERTIES; QUANTITATIVE-ANALYSIS; WHITE-LIGHT; DY3+ IONS; LUMINESCENCE; LIBS; YB3+
In this work, rare earth-doped phosphate glasses were synthesized and characterized using three different spectroscopic techniques. The absorption spectra of the prepared praseodymium (Pr) and samarium (Sm) doped glasses, recorded by a UV-VIS-NIR spectrophotometer, show the characteristic absorption bands of these elements. To confirm this inference, laser-induced fluorescence spectra of Pr and Sm were obtained at a laser excitation of 442 nm. Their emission bands are reported here. The elemental analysis of these samples was carried out using a laser-induced breakdown spectroscopy (LIBS) system. Characteristic emission lines of Pr and Sm have been identified and reported by the recorded LIBS spectra of glass samples. Results prove that using these three complimentary spectroscopic techniques (absorption, fluorescence and LIBS), we can meaningfully characterize rare earth-doped glass samples.
Bioaccumulation; Cadmium; Quantum dots; Laser-Induced Breakdown Spectroscopy; Lemna minor L.; Toxicity;INDUCED BREAKDOWN SPECTROSCOPY; SILVER NANOPARTICLES; BIOLOGICAL APPLICATIONS; ARABIDOPSIS-THALIANA; OXIDE NANOPARTICLES; OXIDATIVE STRESS; IN-VITRO; CADMIUM; GROWTH; CYTOTOXICITY
The purpose of this study was to determine the toxicity of two different sources of cadmium, i.e. CdCl2 and Cd-based Quantum Dots (QDs), for freshwater model plant Lemna minor L. Cadmium telluride QDs were capped with two coating ligands: glutathione (GSH) or 3-mercaptopropionic acid (MPA). Growth rate inhibition and final biomass inhibition of L. minor after 168-h exposure were monitored as toxicity endpoints. Dose-response curves for Cd toxicity and EC50(168h) values were statistically evaluated for all sources of Cd to uncover possible differences among the toxicities of tested compounds. Total Cd content and its bioaccumulation factors (BAFs) in L. minor after the exposure period were also determined to distinguish Cd bioaccumulation patterns with respect to different test compounds. Laser-Induced Breakdown Spectroscopy (LIBS) with lateral resolution of 200 mu m was employed in order to obtain two-dimensional maps of Cd spatial distribution in L. minor fronds. Our results show that GSH- and MPA-capped Cd-based QDs have similar toxicity for L. minor, but are significantly less toxic than CdCl2. However, both sources of Cd lead to similar patterns of Cd bioaccumulation and distribution in L. minor fronds. Our results are in line with previous reports that the main mediators of Cd toxicity and bioaccumulation in aquatic plants are Cd2+ ions dissolved from Cd-based QDs.
Laser induced breakdown spectroscopy; Plasma material interactions; Plasma facing components; Helium retention in tungsten;RECOIL DETECTION; HYDROGEN; SURFACE; EMISSION; ABLATION; ENERGY
Laser-induced breakdown spectroscopy (LIBS) results are presented that provide depth-resolved identification of He implanted in polycrystalline tungsten (PC-W) targets by a 200 keV He+ ion beam, with a surface temperature of approximately 900 degrees C and a peak fluence of 10(23) m(-2). He retention, and the influence of He on deuterium and tritium recycling, permeation, and retention in PC-W plasma facing components are important questions for the divertor and plasma facing components in a fusion reactor, yet are difficult to quantify. The purpose of this work is to demonstrate the ability of LIBS to identify helium in tungsten; to investigate the sensitivity of laser parameters including, laser energy and gate delay, that directly influence the sensitivity and depth resolution of LIBS; and to perform a proof-of-principle experiment using LIBS to measure relative He intensities as a function of depth. The results presented demonstrate the potential not only to identify helium but also to develop a methodology to quantify gaseous impurity concentration in PC-W as a function of depth. (C) 2017 Elsevier B.V. All rights reserved.
Lithium; Toxic level; LIES; Meat;QUANTITATIVE-ANALYSIS; MEAT-PRODUCTS; LITHIUM; SODIUM; MEATBALLS; ADULTERATION; SPECTROMETRY; CONTAMINANTS; ABSORPTION; REDUCTION
The use of Li salts in foods has been prohibited due to their negative effects on central nervous system; however, they might still be used especially in meat products as Na substitutes. Lithium can be toxic and even lethal at higher concentrations and it is not approved in foods. The present study focuses on Li analysis in meatballs by using laser induced breakdown spectroscopy (LIBS). Meatball samples were analyzed using LIBS and flame atomic absorption spectroscopy. Calibration curves were obtained by utilizing Li emission lines at 610 nm and 670 nm for univariate calibration. The results showed that Li calibration curve at 670 nm provided successful determination of Li with 0.965 of R-2 and 4.64 ppm of limit of detection (LOD) value. While Li Calibration curve obtained using emission line at 610 nm generated R-2 of 0.991 and LOD of 22.6 ppm, calibration curve obtained at 670 nm below 1300 ppm generated R-2 of 0.965 and LOD of 4.64 ppm.
Process analytical technology; Process analysers; Film coating; Near-infrared spectroscopy; Raman spectroscopy; Terahertz pulsed imaging; Particle size measurement;OPTICAL COHERENCE TOMOGRAPHY; IN-LINE NIR; PROCESS ANALYTICAL TECHNOLOGY; NEAR-INFRARED SPECTROSCOPY; FLUIDIZED-BED GRANULATION; PARTICLE-SIZE MEASUREMENT; RELEASE COATED PELLETS; RAMAN-SPECTROSCOPY; ACOUSTIC-EMISSION; IMAGE-ANALYSIS
Over the last two decades, regulatory agencies have demanded better understanding of pharmaceutical products and processes by implementing new technological approaches, such as process analytical technology (PAT). Process analysers present a key PAT tool, which enables effective process monitoring, and thus improved process control of medicinal product manufacturing. Process analysers applicable in pharmaceutical coating unit operations are comprehensibly described in the present article. The review is focused on monitoring of solid oral dosage forms during film coating in two most commonly used coating systems, i.e. pan and fluid bed coaters. Brief theoretical background and critical overview of process analysers used for real-time or near real-time (in-, on-, at-line) monitoring of critical quality attributes of film coated dosage forms are presented. Besides well recognized spectroscopic methods (NIR and Raman spectroscopy), other techniques, which have made a significant breakthrough in recent years, are discussed (terahertz pulsed imaging (TPI), chord length distribution (CLD) analysis, and image analysis). Last part of the review is dedicated to novel techniques with high potential to become valuable PAT tools in the future (optical coherence tomography (OCT), acoustic emission (AE), microwave resonance (MR), and laser induced breakdownspectroscopy (LIBS)).
Cama-Moncunill, R. ; Cama-Moncunill, X. ; Casado-Gavalda, M. P. ; Cullen, P. J. ; Jacoby, F. ; Markiewicz-Keszycka, M. ; Sullivan, C.
LIBS; Beef; Brine; Imaging; Spatial;LIBS; QUANTIFICATION; CLASSIFICATION; BEEF; ADULTERATION; SODIUM; TISSUE
This study illustrates the ability of laser induced breakdown spectroscopy (LIBS) to detect and map minerals in food. A LIBS system was used to spatially collect spectra of beef samples. Samples were brined in a 6% salt solution for 2 h and 24 h along with a control sample. Samples were measured by scanning the cross-section of each sample in a 90 x 90 square grid. Sodium (Na) distribution images with respect to emission peak at 589.05 nm were generated after pre-processing the spectral data which directly corresponds to salt levels. As expected, the control sample showed the lowest Na distribution whereas 2 h brined sample showed distribution along the sample's edges decreasing towards the centre. The 24 h brined sample showed increased diffusion. Overall, results show the ability of LIBS to map salt diffusion in meat via Na LIBS imaging, which could be used to optimize brining conditions. (C) 2017 Elsevier Ltd. All rights reserved.
Čelko, L. ; Gadas, P. ; Häkkänen, H. ; Hrdlička, A. ; Kaiser, J. ; Kaski, S. ; Modlitbová, P. ; Novotný, J. ; Novotný, K. ; Prochazka, D. ; Sládková, L.
In general, the detection of F and other halogens is challenging through conventional techniques. In this paper, various approaches for the qualitative and quantitative analysis of F using the laser-induced breakdown spectroscopy (LIBS) technique were demonstrated. In LIBS, fluorine detection can be realized by means of atomic lines and molecular bands. For the purposes of our experiment, two sets of pellets with various contents of CaF2, CaCO3 and cellulose were analyzed using a lab-based LIBS system under a He atmosphere. The fluorine atomic line at 685.60 nm was correlated with CaF signals proving their close relationship. Consequently, the limits of detection were determined for both analytical signals. Moreover, conditions necessary for the quantification of F via CaF band signals were estimated. The dependence of the CaF signal on the varying ratio of Ca and F contents was investigated. Finally, a chip of a real CaF2 crystal was prepared and its surface was mapped with Raman and LIBS systems. The obtained elemental and molecular maps showed good numerical correlations. Thus, the yielded results validated the possibility to substitute the fluorine atomic line by non-conventional CaF molecular bands in the qualitative and quantitative LIBS analysis of fluorine.
Kaiser, J. ; Mikysek, P. ; Novotný, J. ; Novotný, K. ; Pořízka, P. ; Prochazka, D. ; Slobodník, M.
Laser-Induced Breakdown Spectroscopy; Uranium ore; Elements distribution; Self-organizing maps;
This paper presents a novel approach for processing the spectral information obtained from high-resolution elemental mapping performed by means of Laser-Induced Breakdown Spectroscopy. The proposed methodology is aimed at the description of possible elemental associations within a heterogeneous sample. High-resolution elemental mapping provides a large number of measurements. Moreover, typical laser-induced plasma spectrum consists of several thousands of spectral variables. Analysis of heterogeneous samples, where valuable information is hidden in a limited fraction of sample mass, requires special treatment. The sample under study is a sandstone-hosted uranium ore that shows irregular distribution of ore elements such as zirconium, titanium, uranium and niobium. Presented processing methodology shows the way to reduce the dimensionality of data and retain the spectral information by utilizing self-organizing maps (SOM). The spectral information from SOM is processed further to detect either simultaneous or isolated presence of elements. Conclusions suggested by SOM are in good agreement with geological studies of mineralization phases performed at the deposit. Even deeper investigation of the SOM results enables discrimination of interesting measurements and reveals new possibilities in the visualization of chemical mapping information. Suggested approach improves the description of elemental associations in mineral phases, which is crucial for the mining industry.
Kaiser, J. ; Klus, J. ; Mazura, M. ; Novotný, J. ; Novotný, K. ; Pořízka, P. ; Prochazková, P. ; Rebrošová, K. ; Samek, O.
Laser-induced breakdown spectroscopy; Raman spectroscopy; Chemometrics; Bacteria;
In this work, we investigate the impact of data provided by complementary laser-based spectroscopic methods on multivariate classification accuracy. Discrimination and classification of five Staphylococcus bacterial strains and one strain of Escherichia coli is presented. The technique that we used for measurements is a combination of Raman spectroscopy and Laser-Induced Breakdown Spectroscopy (LIBS). Obtained spectroscopic data were then processed using Multivariate Data Analysis algorithms. Principal Components Analysis (PCA) was selected as the most suitable technique for visualization of bacterial strains data. To classify the bacterial strains, we used Neural Networks, namely a supervised version of Kohonen's self-organizing maps (SOM). We were processing results in three different ways - separately from LIBS measurements, from Raman measurements, and we also merged data from both mentioned methods. The three types of results were then compared. By applying the PCA to Raman spectroscopy data, we observed that two bacterial strains were fully distinguished from the rest of the data set. In the case of LIBS data, three bacterial strains were fully discriminated. Using a combination of data from both methods, we achieved the complete discrimination of all bacterial strains. All the data were classified with a high success rate using SOM algorithm. The most accurate classification was obtained using a combination of data from both techniques. The classification accuracy varied, depending on specific samples and techniques. As for LIBS, the classification accuracy ranged from 45% to 100%, as for Raman Spectroscopy from 50% to 100% and in case of merged data, all samples were classified correctly. Based on the results of the experiments presented in this work, we can assume that the combination of Raman spectroscopy and LIBS significantly enhances discrimination and classification accuracy of bacterial species and strains. The reason is the complementarity in obtained chemical information while using these two methods.
Farka, Z. ; Hrdlička, A. ; Jebavá, A. ; Kaiser, J. ; Klus, J. ; Lubal, P. ; Novotný, K. ; Pořízka, P.
Quantum dots; Laser-induced breakdown spectroscopy; Chemical mapping; Filtration paper; Fluorescence microscopy;
In this study, the feasibility of Quantum dots (QDs) 2D distribution mapping on the substrate by Laser-Induced Breakdown Spectroscopy (LIBS) was examined. The major objective of this study was to describe phenomena occurring after applying aqueous solutions of QDs onto filtration paper. Especially, the influence of pH and presence of Cu2 + cations in QDs solutions on LIBS signal was investigated. Cadmium Telluride QDs (CdTe QDs) were prepared by formation of nanosized semiconductor particles in so called “one-pot” synthesis. CdTe QDs were capped by glutathione or by 3-mercaptopropionic acid. The technique described in this work allows detection of QDs injected on the selected substrate – filtration paper. Results obtained from LIBS experiments were collated with a comparative method, fluorescence microscopy, which showed variations in the distribution of QDs on the substrate surface and possibilities for quenching. Due to the immediate signal response, relatively simple instrumentation and automatization possibility, LIBS offers promising and fast alternative to other techniques, as it is able to detect also nanoparticles with no visible luminescence.
Čelko, L. ; Hrdlička, A. ; Kaiser, J. ; Novotný, K. ; Pořízka, P. ; Prochazka, D. ; Remešová, M. ; Škarková, P.
Laser-Induced Breakdown Spectroscopy; Silver nanoparticles; Low pressure conditions; Sensitivity improvement;
In this work we studied the effect of vacuum (low pressure) conditions on the behavior of laser-induced plasma (LIP) created on a sample surface covered with silver nanoparticles (Ag-NPs), i.e. Nanoparticles-Enhanced Laser-Induced Breakdown Spectroscopy (NELIBS) experiment in a vacuum. The focus was put on the step by step optimization of the measurement parameters, such as energy of the laser pulse, temporally resolved detection, ambient pressure, and different content of Ag-NPs applied on the sample surface. The measurement parameters were optimized in order to achieve the greatest enhancement represented as the signal-to-noise ratio (SNR) of NELIBS signal to the SNR of LIBS signal. The presence of NPs involved in the ablation process enhances LIP intensity; hence the improvement in the analytical sensitivity was yielded. A leaded brass standard was analyzed with the emphasis on the signal enhancement of Pb traces. We gained enhancement by a factor of four. Although the low pressure had no significant influence on the LIP signal enhancement compared to that under ambient conditions, the SNR values were noticeably improved with the implementation of the NPs.
Burget, R. ; Kaiser, J. ; Klus, J. ; Mašek, J. ; Modlitbová, P. ; Novotný, J. ; Novotný, K. ; Prochazka, D. ; Rajnoha, M.
Laser-Induced Breakdown Spectroscopy; ;
In this work, we proposed a new data acquisition approach that significantly improves the repetition rates of Laser-Induced Breakdown Spectroscopy (LIBS) experiments, where high-end echelle spectrometers and intensified detectors are commonly used. The moderate repetition rates of recent LIBS systems are caused by the utilization of intensified detectors and their slow full frame (i.e. echellogram) readout speeds with consequent necessity for echellogram-to-1D spectrum conversion (intensity vs. wavelength). Therefore, we investigated a new methodology where only the most effective pixels of the echellogram were selected and directly used in the LIBS experiments. Such data processing resulted in significant variable down-selection (more than four orders of magnitude). Samples of 50 sedimentary ores samples (distributed in 13 ore types) were analyzed by LIBS system and then classified by linear and non-linear Multivariate Data Analysis algorithms. The utilization of selected pixels from an echellogram yielded increased classification accuracy compared to the utilization of common 1D spectra.
Heitz, J. ; Jasik, J. ; Lackner, J. ; Parigger, C. G. ; Pedarnig, J. D. ; Spendelhofer, W. ; Veis, P.
Laser-induced breakdown spectroscopy; LIBS; Polyethylene; Rubber from tire production; Molecular emission spectroscopy; Rotational-vibrational analysis;
INDUCED BREAKDOWN SPECTROSCOPY; FEMTOSECOND LASER; NANOSECOND; DYNAMICS
Besides Raman spectroscopy, laser induced breakdown spectroscopy (LIBS) can provide standoff detection of trace chemicals at longer distances by applying filamentation techniques and using femtosecond rather than nanosecond pulses.
Laser-induced breakdown spectroscopy; tissue ablation; soft tissue; classification; principal component analysis; k nearest neighbors; confusion matrix; pork;BIOMEDICAL APPLICATIONS
Classification of pork soft tissues, including skin, fat, loin, tenderloin and ham muscles, was achieved using combination of laser-induced breakdownspectroscopy, principal component analysis and k nearest neighbors classification.
LIBS; Bacteria; Neural network; K-means; Spectroscopy;LIBS
LIBS technique was used to obtain spectra of Escherichia coli and Staphylococcus aureus for identifying characteristic emission lines and then they were analyzed by K-means classifier for neural network feasibility. The potential of this method for bacteria identification was demonstrated.
Capacitor; Tantalum; LIBS; Multipulse; Nd:YAG laser;INDUCED BREAKDOWN SPECTROSCOPY; ABLATION; LIBS
In this paper a method for cleaning tantalum capacitors terminals, using the technique of selective ablation by pulsed laser is proposed. Such ablation is studied by the LIBS technique to characterize capacitors and determine the resin composition and possible contaminants adhered. In addition, OCT measurements are performed to recreate the damage done to the samples.
Liquid lithium corrosion; Corroded layer; Depth profiling; LIBS; Refined grains enhanced;INDUCED PLASMA; QUANTITATIVE-ANALYSIS; SURFACE-TOPOGRAPHY; MASS-SPECTROMETRY; EUTECTIC PB-17LI; ABLATION; BEHAVIOR; SAMPLES; HELIUM; CURVES
Liquid metal lithium cause severe corrosion on the surface of metal structure material that used in the blanket and first wall of fusion device. Fast and accurate compositional depth profile measurement for the boundary layer of the corroded specimen will reveal the clues for the understanding and evaluation of the liquid lithium corrosion process as well as the involved corrosion mechanism. In this work, the feasibility of laser-induced breakdown spectroscopy for the compositional depth profile analysis of type 316 stainless steel which was corroded by liquid lithium in certain conditions was demonstrated. High sensitivity of LIBS was revealed especially for the corrosion medium Li in addition to the matrix elements of Fe, Cr, Ni and Mn by the spectral analysis of the plasma emission. Compositional depth profile analysis for the concerned elements which related to corrosion was carried out on the surface of the corroded specimen. Based on the verified local thermodynamic equilibrium shot-by-shot along the depth profile, the matrix effect was evaluated as negligible by the extracted physical parameter of the plasmas generated by each laser pulse in the longitudinal depth profile. In addition, the emission line intensity ratios were introduced to further reduce the impact on the emission line intensity variations arise from the strong inhomogeneities on the corroded surface. Compositional depth profiles for the matrix elements of Fe, Cr, Ni, Mn and the corrosion medium Li were constructed with their measured relative emission line intensities. The distribution and correlations of the concerned elements in depth profile may indicate the clues to the complicated process of composition diffusion and mass transfer. The results obtained demonstrate the potentiality of LIBS as an effective technique to perform spectrochemical measurement in the research fields of liquid metal lithium corrosion. 2017 Elsevier B.V. All rights reserved.
plasma-material interactions; plasma diagnostic techniques; laser induced breakdown spectroscopy; laser induced ablation spectroscopy;FUSION DEVICES; COMPONENTS
A laser based method combined with spectroscopy, such as laser-induced breakdown spectroscopy and laser-induced ablation spectroscopy , is a promising technology for plasma-wall interaction studies. In this work, we report the development of in situ laser-based diagnostics for the assessment of static and dynamic fuel retention on the first wall without removing the tiles between and during plasma discharges in the Experimental Advanced Superconducting Tokamak . The fuel retention on the first wall was measured after different wall conditioning methods and daily plasma discharges by in situ LIBS. The result indicates that the LIBS can be a useful tool to predict the wall condition in EAST. With the successful commissioning of a refined timing system for LIAS, an in situ approach to investigate fuel retention is proposed.
laser-induced breakdown spectroscopy; plasma wall interaction; fuel retention; deposition; erosion;
Laser-induced breakdown spectroscopy is a well-established elemental composition analysis method as well as one of the most promising candidates for in situ first wall diagnosis of fusion devices. In this work, limiter graphite tiles, which were exposed in the initial operational phase of the Wendelstein 7-X stellarator to He and H plasma, are analyzed ex situ by LIBS employing a picosecond pulsed laser for the first time and compared with post mortem analysis techniques. Depth profiles of each element and 2D profile of the ratio of H and C atoms on the surface are investigated. Both H content and retention depth on the deposition dominated zone are higher than on the erosion dominated zone due to the formation of C-H co-deposition layer. The results from LIBSare in agreement with those from the cross-sectional scanning electron microscopic image and electron dispersive x-ray spectroscopy.
laser induced breakdown spectroscopy; spatial regularities of the laser-induced plasma plume; detection of hydrogen isotopes;EROSION/DEPOSITION; SPECTROSCOPY
ITER plans foresee the quantitative diagnostics of fuel retention in reactor walls at nearatmospheric pressures. Using laser induced breakdown spectroscopy for this purpose assumes a reliable resolving of Balmer a-lines of hydrogen isotopes in spectra of plasma produced by focused laser radiation onto the target surface. To develop LIBS for quantitative diagnostics of fuel retention during the maintenance breaks of ITER, the effect of background gas pressure on the laser-induced plasma characteristics has been studied. The background pressure limits the expansion rate of plasma and as a result it leads to higher plasma concentrations. At the same time the limiting factor of the resolving of hydrogen isotope lines is the lines broadening by Stark effect, which is the function of electron concentration. The resolving of lines become possible recording spectra at longer delay times after the laser pulse. On the other hand, at longer delays the signal-to-noise ratio decreases. As a compromise, we found that at atmospheric pressure and at delay times > 2000 ns, a fitting of H a and D a lines by Voigt contours allows a reliable discrimination of these lines.
Ferri, J. M.
Halloysite nanotubes; Lumen enlargement; Acid treatment; Catalysis; LIBS;CLAY NANOTUBES; TREATED HALLOYSITE; CONTROLLED-RELEASE; CARBON NANOTUBES; NANOCOMPOSITES; ADSORPTION; LUMEN; SEPARATION; OXIDATION; DELIVERY
Halloysite nanotubes are a type of naturally occurring inorganic nanotubes that are characterized by a different composition between their external and internal walls. The internal walls are mainly composed of alumina whilst external walls are composed of silica. This particular structure offers a dual surface chemistry that allows different selective surface treatments which can be focused on increasing the lumen, increasing porosity, etc. In this work, HNTs were chemically treated with different acids , for 72 h at a constant temperature of 50 degrees C. As per the obtained results, the treatment with sulphuric acid is highly aggressive and the particular shape of HNTs is almost lost, with a remarkable increase in porosity. The BET surface area increases from 52.9 up to 132.4 m g with sulphuric acid treatment, thus showing an interesting potential in the field of catalysis. On the other hand, the treatment with acetic acid led to milder effects with a noticeable increase in the lumen diameter that changed from 13.8 nm up to 18.4 nm which the subsequent increase in the loading capacity by 77.8%. The aluminium content was measured by X-ray fluorescence and laser induced breakdown spectroscopy . The final results using two systems, suggest a good correlation between the acid strength and the aluminium reduction. Consequently, is possible to conclude that new applications for HNTs can be derived from selective etching with acids. Sulphuric acid widens the potential of HNTs in the field of catalysis while weak acids such as acetic and acrylic acids give a controlled and homogeneous lumen increase with the corresponding increase in the loading capacity.
IODINE; DIAGNOSIS; PROTEIN; LEVEL
The thyroid is an important hormone regulation organ. Laser induced breakdown spectroscopy is developed to assess iodine and other essential elements in the thyroid . Subjects are administered 0.05% iodine water for 0, 6, and 12 days before the thyroid is extracted. Pronounced iodine, sodium, calcium, and potassium emissions are observed at approximately 746, 589, 395/422, and 766/770 nm, respectively. Iodine emission is surprisingly highest in 0 day subjects, lowest after 6 days, and recovers by 12 days. This follows the Wolff-Chaikoff effect as ingestion of excess iodine reduces thyroid iodine and iodine is essential for hormone production. LIBS is a promising method for trace elemental analysis of the thyroid.
Virgin Eleusa; Polish-Lithuanian Commonwealth; Art materials study; SERS; Inorganic pigments; Micro-FTIR; Layer-by-layer LIBS;INDUCED BREAKDOWN SPECTROSCOPY; RAMAN-SCATTERING; CRETAN SCHOOL; IDENTIFICATION; PIGMENTS; SERS; ENHANCEMENT; ICONOGRAPHY; SURFACE; CANVAS
Here the results are reported on the multi-analytical study of the Belarusian icon ""Virgin Eleusa"" . The X-ray and luminescence studies revealed some interventions performed in different time periods. The materials of original painting as well as the materials of interventions were successfully characterized by spectroscopic techniques. Layer-by-layer Laser induced breakdown spectroscopy was used for elemental composition study of art materials. Fourier-transform infrared microspectroscopy was used to indicate the types of binding media in the grounds and paint layers as well as to identify the art pigments. A low concentration of cerulean and cadmium yellow in the upper paint layers were identified by Surface enhanced Raman scattering . Since cerulean and cadmium yellow are known to come into use in XIX cent., the SERS results played the crucial role for dating of some intervention.
MACHINE REGRESSION-MODEL; CONVEX-OPTIMIZATION; COEFFICIENTS; LIBS
In quantitative laser-induced breakdown spectroscopy analysis, spectral signals are usually represented by the linear combination of characteristic peaks with useful spectral information and unwanted noise components. All of the existing regression analysis methods are related to a spectral data matrix, which is composed of certified samples with different spectral intensity. Therefore, spectral data matrix processing is critical for quantitative LIBS analysis. A prevalent assumption when constructing a matrix approximation is that the partially observed matrix is of low-rank. Moreover, the low-rank structure always reflects the useful information and is regarded as a powerful data preprocessing method. In this paper, a novel and quantitative LIBS analysis method based on a sparse low-rank matrix approximation via convex optimization is proposed. Based on the sparsity of the spectral signals, we present a convex objective function consisting of a data-fidelity term and two parameterized penalty terms. To improve the accuracy of the quantitative analysis, a new non-convex and non-separable penalty based on the Moreau envelope is proposed. Then, the alternating direction method of multipliers algorithm was utilized to solve the optimization problem. The proposed method was applied to the quantitative analysis of 23 high alloy steel samples. Both of the performances of the Partial Least Squares and Support Vector Machine regression models are improved by using the low-rank matrix approximation scheme, which proves the effectiveness of the proposed method.
SPECTRAL-LINE; EMISSION-LINES; INDUCED FLUORESCENCE; RESONANCE LINES; INDUCED PLASMAS; COEFFICIENTS; PRESSURE; ALUMINUM; CALIBRATION; LIBS
Reducing self-absorption is one of the most important steps in achieving accurate analyses in laser-induced breakdown spectroscopy . In this work, LIBSassisted with laser-stimulated absorption was used to reduce self-absorption effects in LIBS. A wavelength-tunable laser was used to resonantly excite cold atoms and reduce their amount in laser-induced plasmas, and thus fewer cold atoms at the plasma periphery re-absorb light from the plasma center. Accordingly, the self-absorption effect was reduced. Copper and chromium elements in steels were taken as examples to evaluate and compare the self-absorption effects in LIBS and LSA-LIBS. The results of calculated self-absorption coefficients supported the effectiveness in reducing self-absorption and improving analytical linearity using LSA-LIBS.
INDUCED BREAKDOWN SPECTROSCOPY; SUPPORT VECTOR MACHINES; PARTIAL LEAST-SQUARES; DISCRIMINANT-ANALYSIS; SUBSET-SELECTION; LASER; CLASSIFICATION; SAMPLES; IDENTIFICATION; ALGORITHM
In recent years, LIBS quantitative analysis based on multivariate regression has received considerable attention, and variable selection is critical for improving accuracy of multivariate regression analysis of LIBS. In the present study, sequential backward selection combined with random forest was proposed to improve detection accuracy of sulfur and phosphorus in steel. First, LIBS spectrum line of S and P was identified by the NIST database. Second, input variables for RF calibration model were selected and optimized by SBS, and RF model parameters and m) were optimized by out-of-bag estimation. Finally, optimized input variables and model parameters were employed to build an SBS-RF calibration model for quantitative analysis of P and S in steel. Results showed that the SBS-RF model provided good predictions for S and P compared with those provided by the univariate method, PLS model and traditional RF model. Thus, LIBS coupled with SBS-RF is an effective method for quality supervision and control of steel products.
ARTIFICIAL NEURAL-NETWORK; ICP-MS; LASER; LIBS; PLASMA; MATRIX; MODEL
Laser-induced breakdown spectroscopy can be used for measuring the concentrations or ratios of various trace elements in solid samples. A laser pulse with a 532 nm wavelength, 5 ns pulse duration, 100 mm beam spot diameter, and 30 mJ single pulse energy is used for ablating the United States Geological Survey series of geological standard samples. The concentrations of iron in different geological samples are obtained using artificial neural networks. In addition, the influence of matrix effects on the measurement error is analyzed. Experimental results reveal that the relative errors of BCR-1G, BHVO-2G, BIR-1G, GSD-1G, and GSE-1G between the measured concentrations and the certified concentrations are 1.86%, 5.73%, 0.27%, 3.86%, and 2.63%, respectively, which indicate that the LIBS method using back propagation artificial neural networks can effectively determine the iron concentrations of USGS geological standard samples. The matrix effects of standard samples are analyzed, which shows that the matrix effects of GSD-1G and GSE-1G are more different than others. As a result, some significant measurement errors in concentration determination resulted from different matrix effects.
INDUCED BREAKDOWN SPECTROSCOPY; LASER-INDUCED FLUORESCENCE; SOLID-PHASE EXTRACTION; ICP-MS; QUANTITATIVE-ANALYSIS; LIQUID SAMPLES; METAL ANALYSIS; ULTRASONIC NEBULIZATION; ATOMIC FLUORESCENCE; AQUEOUS-SOLUTION
To realize ultrasensitive detection of trace amounts of lead in water, laser-induced breakdown spectroscopy combined with laser-induced fluorescence was investigated. A wood-slice substrate was selected: as a water absorber to convert liquid-sample analysis to solid-sample analysis; to eliminate the influence of a water matrix to spectral analysis in the plasma during direct analysis of water samples. The wood slice after treatment was ablated by a Q-switched Nd:YAG laser to produce plasma. Then, the lead atoms in the plasma were re-excited by a second tunable dye laser resonantly. The LIF signal of lead was detected to improve its sensitivity to spectral analysis significantly. Under the assistance of this matrix-converting method, the calibration curve of lead in water samples was created and the limit of detection was found to be 0.32 ppb, two orders of magnitude better than that obtained by analyzing water samples directly using the same LIBS-LIF technique. This sample-pretreatment procedure was rapid and easy to handle. Upon combination with LIBS-LIF, ultrasensitive detection of trace amounts of toxic metal elements in water could be realized. This approach could be applied in water-quality control and monitoring of environmental pollution.
Laser induced breakdown spectroscopy; Lanthanides; Quantitative analysis;RARE-EARTH-ELEMENTS; PLASMA-MASS SPECTROMETRY; NEUTRON-ACTIVATION ANALYSIS; QUANTITATIVE-ANALYSIS; AQUEOUS-SOLUTION; LIBS LIMIT; WASTE SALT; SAMPLES; OXIDE; WATER
Quantitative analysis of Pr, Nd, Ce, La and Sm were carried out simultaneously in LiF-KCl matrix using laser induced breakdown spectroscopic technique. Two non-interfering analytical emission lines have been identified for each lanthanide and using the internal standard method, the calibration curve is constructed from 0.3 to 5% for Pr, Nd, Ce and La and from 0.3 to 3% for Sm. Both the emission lines showed good regression coefficient ) ranging from 0.9953 to 0.9996. The analytical capability of this method is studied through the correlation uncertainty of measured values with its known value in synthetic samples containing all the lanthanides in equal amount . Low value of correlation uncertainty confirms that LIBS has a great potential for quantitative analysis of lanthanides in LiF-KCl matrix.
Laser-induced breakdown spectrometry; X-ray fluorescence spectrometry; Chromium; Surface layer; Steel sheets;DEPTH PROFILE ANALYSIS; GALVANIZED STEEL; COATED STEEL; ABLATION; SPECTROSCOPY; COPPER
A method was proposed for the determination of Cr in a thin surface nanolayer deposited on top of a micrometrical Zn-based anticorrosive coating of steel sheets using laser-induced breakdown spectrometry . Optimization of the LIBS parameters was performed with respect to the statistical parameters of regression, these being the coefficient of determination , akaike information criterion and mean-squared prediction error. These were calculated for curves describing the relationship between the Cr surface concentration and the intensity of LIBS signal. The most critical parameter of analysis appears to be the focal spot diameter. When its value was 200 mu m and corresponding energy density had value of 413.8 J/cm, the intensity-concentration relationship revealed a negative slope. This phenomenon was caused by the difference in total ablated volume for samples with a different content of Cr in the surface layer. This phenomenon was not observed for higher values of the focal spot diameter and lower values of fluence ). A range of calibration obtained under optimal conditions was 11-21 mg/m and the limit of detection was 0.7 mg/m. The recovery values calculated from the results of the proposed LIBS method and the standard ED XRF method ranged from 99.2 to 101%.
Portable laser-induced breakdown spectroscopy (LIES); Chemometric analysis; Hazardous elements (HEs); Suspended particulates matter (SPM); Storm event;SURFACE BOTTOM SEDIMENTS; SPECTROSCOPY; CALCIUM; FLUXES; METALS; LIBS
The main objective of this work is to provide researchers with a fast methodology of analysis capable to assess water quality in an urban river catchment during extreme rainfall events without previous elemental quantification. The analytical methodology combines measurement with portable laser-induced breakdown spectroscopy (LIBS) and direct chemometric treatment of the LIBS spectra. With this aim, suspended particular matter (SPM) samples were collected during five storm events, every 2 h with an automatic water sampler in three control points (gauging stations) of an urban river (Deba River, Basque Country, Spain). SPM samples were analyzed in situ by a handheld laser induced breakdown spectrometry (HH-LIBS), and the complete LIBS spectra were statistically analyzed by Principal Component Analysis (PCA) after outlier identification by k-nearest neighbors (kNN). The PCA results showed differentiation between monitored localizations and the period when the storm event occurred. It was also possible to identify important discriminant variables, some of them corresponding to hazardous elements such as Pb, Cr, Ni, and Cu. Basing on the correlation between variables, it was possible to identify their sources (urban/municipal contamination, anthropogenic activities, etc.). Moreover, thanks to this methodology, it was possible to predict the mobilization of hazardous elements at the end of a storm event and determine the environmental risk assessment in an urban river.
INDUCED BREAKDOWN SPECTROMETRY; INDUCED PLASMA SPECTROMETRY; JEWELRY INDUSTRY; SPECTROSCOPY; METALS; STEEL
In this study, galvanic coatings of Cu and Ni, typically applied in industrial standard routines, were investigated. Ablation experiments were carried out using the first two harmonic wavelengths of a pulsed Nd: YAG laser and the resulting plasma spectra were analysed using a linear Pearson correlation method. For both wavelengths the absorption/ablation behaviour as well as laser-induced breakdown spectroscopy (LIBS) depth profiles were studied varying laserfluences between 4.3-17.2 J/cm(2) at 532 nm and 2.9-11.7 J/cm(2) at 1064 nm. The LIBS-stratigrams were compared with energy-dispersive X-ray spectroscopy of cross-sections. The ablation rates were calculated and compared to theoretical values originating from a thermal ablation model. Generally, higher ablation rates were obtained with 532 nm light for both materials. The light-plasma interaction is suggested as possible cause of the lower ablation rates in the infrared regime. Neither clear evidence of the pure thermal ablation, nor correlation with optical properties of investigated materials was obtained.
SPECTRUM STANDARDIZATION; QUANTITATIVE-ANALYSIS; LIBS; NORMALIZATION; SIGNAL; MODEL
The uncertainty of collected spectral data is one of the most important issues for the application of laser-induced breakdown spectroscopy (LIBS) quantitative analysis. The fluctuation of the target surface simultaneously affects both the focus depth of the laser beam and the relative collection position, either of which may lead to severe fluctuation of the spectral signal. Thus, in this study, for detecting and reducing the fluctuation, an imaging system was deployed to monitor the plasma, and a mathematical model was also built based on both spectral signal and positional information. An ICCD camera was used to record the image of the plasma so as to detect the plasma and acquire positional information. Furthermore, the relationship between plasma position and specific spectral line intensity was obtained by the fitting function. Five aluminium alloy samples were employed to validate the reliability of the proposed method. As a result, the average RSDs of the samples (with a position fluctuation range of about 2 mm) in different spectral lines (Si 288.15 nm, Fe 273.95 nm, Cu 324.75 nm, Mn 259.37 nm and Mg 280.27 nm) were reduced from 34.57%, 38.86%, 31.05%, 39.74%, and 36.91% (without normalization) to 4.63%, 6.84%, 5.64%, 7.64%, and 4.83% (with the combination method presented in this paper), respectively; the determination coefficients (R-2) reached 0.996, 0.999, 0.989, 0.999, and 0.9999, respectively. These results prove that the proposed method can both improve measurement reliability and guarantee measurement accuracy.
Laser-induced plasma; Equivalence ratio; Plasma emission; Spray flame;LASER-INDUCED BREAKDOWN; EQUIVALENCE RATIO MEASUREMENT; TO-AIR RATIO; INDUCED SPARK; GAS-DENSITY; SPECTROSCOPY; METHANE; MIXTURE; PRESSURE; IGNITION
A portable device composed of photodiodes and bandpass filters was developed to measure local fuel concentration in a liquid hydrocarbon-fueled spray flame. The plasma emission spectra in and around the flame were selectively captured using such simplified device or plug instead of using a laboratory standard laser-induced breakdown spectroscopy (LIES) system consisting of an ICCD and a spectrometer. The hydrogen (656 nm) and oxygen (777 nm) atomic lines were selected to determine the fuel concentration in atmospheric pressure. The WO signal intensity ratio was found to be a strong function of the fuel concentration, and thus a calibration curve for the concentration measurements was established and validated using conventional LIES. The proposed scheme to measure the local equivalence ratio of spray flames using a bundled layout of multiple LIES plugs alongside the combustor wall may offer simple and highly robust diagnostics, especially under the harsh combustion conditions within air breathing engines. (C) 2017 Elsevier Ltd. All rights reserved.
Azimi, H. ; Hannagan, R. ; Howe, G. ; Nagarajan, R. ; Ponrathnam, T. ; Robertson, S. ; Ryan, D. ; Sullivan, C. ; Yu, S. R.
Heavy metals; Detection; Voltammetry; Environmental testing; Field characterization; E-Tongue; Arsenic; Cadmium; Lead; Mercury; Zinc;INDUCED BREAKDOWN SPECTROSCOPY; ANODIC-STRIPPING VOLTAMMETRY; SCREEN-PRINTED ELECTRODES; ORGANIC POLYMERS; SOILS; GROUNDWATER; SYSTEM; FLUORESCENCE; ENVIRONMENT; SUBSURFACE
Heavy metals from both natural and anthropogenic sources present a significant risk to human and environmental health. A number of methods have been developed for the detection and quantification of heavy metals. These methods include laboratory analysis, onsite testing of samples, and in situ techniques. This paper will review current and emerging technologies for site characterization with a specific focus on in situ detection of heavy metal contamination in geoenvironmental remediation projects. In addition, on-going research performed for the development of an in situ voltammetric sensor system will be presented. A number of devices exist for the efficient sampling of contaminated groundwater including the Hydropunch, BAT system, and Cone Sipper. Samples may either be sent to a laboratory for analysis with techniques such as atomic absorption spectroscopy, inductively coupled plasma-mass spectrometry, atomic emission spectroscopy, and X-ray fluorescence, or analyzed onsite using methods such as colorimetry, voltammetry, or biological based chemical sensors. For in situ analysis of heavy metals in soil, X-ray fluorescence and laser induced breakdown spectroscopy technologies have been integrated with the cone penetrometer probe. This paper further explores the feasibility of integrating electrochemical techniques based on voltammetry for the in situ detection of aqueous metal ions. The development of bismuth, gold nanoparticle, and polymer modified electrodes allow for the detection of heavy metal contaminants, including lead, cadmium, mercury and arsenic, at low part per billion levels.
Aluminium beverage can; Life Cycle Assessment; Recycling; Solid state recycling; Laser induced breakdown spectroscopy; Abiotic resource depletion;LIFE-CYCLE ASSESSMENT; IMPACT ASSESSMENT; ALLOY SCRAP; WASTE; ECONOMY; SYSTEMS; LOOP; METHODOLOGY; COLLECTION; MANAGEMENT
It is undisputed that the recycling of aluminium is desirable as long as the environmental and economic implications of its reintegration do not exceed the burdens of its primary production. The efficiency of any aluminium recycling system can be expressed by the total material losses throughout the entire process chain, ideally reaching 0%, thus equivalent to 100% metal recovery. However, in most cases metals are recycled in open/cascade recycling loop where dilution and quality losses occur. Innovations in aluminium beverage can (ABC) design as well as in sorting and recycling technologies have the potential to increase recyclability and avoid downcycling issues due to mixed alloy scrap streams. By means of Life Cycle Assessment (LCA) seven scenarios, comprising specific systemic changes, are compared to the current recycling practice of the used beverage can in the UK. The End-of-Life modelling of recycling is performed in accordance with the equal share method to account for impacts both on the recyclability and the recycled content. The results confirm the primary aluminium production and energy consumption in the ABC production as the hotspots in the life cycle of the ABC. The toxicity and energy-related impact categories show the highest susceptibility to increasing recycled content and recycling rate, while the technological novelties show little effect. In terms of abiotic resource depletion the introduction of novel technologies could have the potential to retain quality of the aluminium alloys by either establishing dedicated waste streams or upgrading the aluminium scrap by dedicated sorting strategies.
MINERALS; ELEMENTS; SAMPLES; WATER; PB
On-stream analysis of the element content in ore slurry has important significance in the control of the flotation process and full use of raw materials. Therefore, techniques that can monitor the chemistry in slurries online are required. Laser-induced breakdown spectroscopy (LIBS) is one of the potential approaches to online measurements due to its capability of in situ and real-time analysis. However, using LIBS for on-stream analysis of slurries is challenging due to the issues such as surface ripples, sample splashing, sedimentation, etc. To address these problems, we developed a slurry circulation system. The effects of slurry flow rate on LIBS spectra were investigated to achieve the optimal detecting surface for better repeatability of LIBS. The coefficient of determination R-2 of the calibration curve for Fe element is 0.982, and the limit of detection of Fe element was estimated to be 0.075 wt. % under the optimized experimental parameters. The results show that this slurry circulation system is applicable to the on-stream slurry analysis. (C) 2017 Optical Society of America
INDUCED BREAKDOWN SPECTROSCOPY; STAINLESS-STEEL; PROPAGATION; REMOVAL; MEDIA
High Energy Lasers (HELs) used for defense applications require operational distances ranging from few hundred meters to several kilometers. As the distance increases, the incident beam properties and, consequently, the anticipated effect delivered to the sample become less predictable. Therefore, the direct observation of the event induced by the laser can become an asset. In this paper, we propose a novel spectroscopic method that analyses in real time the spectral components present in the flames produced during the interaction of a HEL with a metallic piece at a long distance. This method was used on aluminum and carbon steel samples placed 200 m away from the laser system. It was discovered that the aluminum and iron oxides created as a by-product of the HEL reaction with the samples emitted clear fingerprint signatures that could be detected remotely using a spectroscopic receiver placed beside the HEL beam director. The real-time assessment of the laser-induced effect can be achieved by monitoring the temporal evolution of the oxide signatures, hence providing information to the operator about the reaction and the nature of the sample illuminated.
laser induced breakdown spectroscopy; electron density; plasma temperature; malignant tissue; quadrupole-mass spectroscopy;Q-SWITCHED NDYAG; OPTICAL-EMISSION; ORAL-CANCER; IN-VIVO; CARCINOMA; FLUORESCENCE; CONFINEMENT; ELEMENTS; PLASMAS; SITU
Here, the authors have utilized laser induced breakdown spectroscopy (LIBS) to distinguish cancerous tissues from normal ones. For this purpose, the plasma emission spectra of the normal and cancerous tissues taken from four different organs of interest, i.e, breast, colon, larynx, and tongue are analyzed via the excitation of a pulsed Neodymium-doped Yttrium Aluminum Garnet (ND: YAG) laser at 1064 nm. Results show that the abundance of the trace elements such as Ca, Mg, and Na trace elements are elevated in the cancerous tissues with respect to normal ones. In addition, inductively coupled plasma-optical emission spectroscopy and quadrupole-mass spectroscopy are employed to support the findings given by LIBS. Furthermore, the plasma characteristics such as temperature and electron density are probed by data processing of the plasma spectra at local thermal equilibrium condition as an alternative technique to discriminate between the normal and malignant tissues. It is shown that more energetic plasma is created on the neoplastic specimens resulting in higher electron density and plasma temperature due to the corresponding intense atomic/ionic characteristic emissions of species. The simplicity and low cost of processes benefits the physicians to encourage the clinical application of LIBS in near future. (C) 2017 Laser Institute of America.
RARE-EARTH-ELEMENTS; COLLOIDS; LIQUIDS
In this paper, we report the use of laser induced breakdown spectroscopy (LIBS) to detect dissolved Eu and Yb in bulk aqueous solutions. Ten strong emission lines of Eu and one strong emission line of Yb were identified in the underwater LIBS spectra obtained by using Czerny-Turner spectrometer within the wavelength range of 375-515 nm, Temporal evolution of plasma and the effect of laser pulse energy on the spectral emission were studied. Calibration curves using the concentration range from 500 to 10,000 ppm were developed and limits of detection for Eu and Yb were estimated to be 209 and 156 ppm, respectively. (C) 2017 Elsevier B.V. All rights reserved.
Bousquet, B. ; Cousin, A. ; Dehouck, E. ; Fabre, C. ; Forni, O. ; Frydenvang, J. ; Gasnault, O. ; Lacour, J. L. ; Lasue, J. ; Maurice, S. ; Meslin, P. Y. ; Wiens, R. C.
LIBS; Water; Hydrogen; ChemCam; Mars; Low pressure; Roughness;CHEMCAM INSTRUMENT SUITE; QUANTITATIVE-ANALYSIS; INDUCED DESORPTION; SOLID-SURFACES; INDUCED PLASMA; LOW-PRESSURES; GALE CRATER; MARS; CONFINEMENT; IMPROVEMENT
On Mars, Laser-Induced Breakdown Spectroscopy CUBS) as performed by the ChemCam instrument can be used to measure the hydrogen content of targets in situ, under a low pressure CO2 atmosphere. However, unexpected variations observed in the Martian dataset suggest an effect related to target roughness. Here, we present a series of laboratory experiments that reproduce the effect observed on Mars and explore possible causes. We show that the hydrogen peak intensity increases significantly with increasing exposure of the target surface to the LIBS plasma, and that these variations are specific to hydrogen, as other emission lines in the spectra are not affected. The increase of the signal could be related to an addition of hydrogen to the plasma due to interaction with the surrounding target surface, yet the exact physical process to explain such effect remains to be identified. More generally, this effect should be taken into account for the quantification of hydrogen in any LIBS applications where the roughness of the target is significant. (C) 2017 Elsevier B.V. All rights reserved.
Libs; Lithium; Forsterite; Real-time analysis;
A factor of lithium distribution between single-crystal forsterite (Cai:Mg2SiO4) and its melt are studied by laser-induced breakdown spectroscopy. Lithium content in the crystalline phase is found to achieve a saturation at relatively low Li concentration in the melt (about 0.02%wt.). An algorithm and software are developed for real-time analysis of the studied spectra of lithium trace amounts at wide variation of the plasma radiation intensity. The analyzed plasma spectra processing method is based on the calculation of lithium emission part in the total emission of the target plasma for each recorded spectrum followed by the error estimation for the series of measurements in the normal distribution approximation. (C) 2017 Elsevier B.V. All rights reserved.
De Ninno, A.
Laser induced breakdown spectroscopy LIBS; Plasma; Calibration; Matrix effect; Particles;INDUCED BREAKDOWN SPECTROSCOPY; ELEMENTAL ANALYSIS; QUANTITATIVE-ANALYSIS; SAMPLES; NORMALIZATION; PARAMETERS; AEROSOLS; LIBS
The laser induced plasma spectroscopy was applied on particles attached on substrate represented by a silica wafer covered with a thin oil film. The substrate itself weakly interacts with a ns Nd:YAG laser (1064 nm) while presence of particles strongly enhances the plasma emission, here detected by a compact spectrometer array. Variations of the sample mass from one laser spot to another exceed one order of magnitude, as estimated by on-line photography and the initial image calibration for different sample loadings. Consequently, the spectral lines from particles show extreme intensity fluctuations from one sampling point to another, between the detection threshold and the detector's saturation in some cases. In such conditions the common calibration approach based on the averaged spectra, also when considering ratios of the element lines i.e. concentrations, produces errors too large for measuring the sample compositions. On the other hand, intensities of an analytical and the reference line from single shot spectra are linearly correlated. The corresponding slope depends on the concentration ratio and it is weakly sensitive to fluctuations of the plasma temperature inside the data set. A use of the slopes for constructing the calibration graphs significantly reduces the error bars but it does not eliminate the point scattering caused by the matrix effect, which is also responsible for large differences in the average plasma temperatures among the samples. Well aligned calibration points were obtained after identifying the couples of transitions less sensitive to variations of the plasma temperature, and this was achieved by simple theoretical simulations. Such selection of the analytical lines minimizes the matrix effect, and together with the chosen calibration approach, allows to measure the relative element concentrations even in highly unstable laserinduced plasmas. (C) 2017 Elsevier B.V. All rights reserved.
Laser induced breakdown spectroscopy (LIBS); On-line analysis; Heavy metal; Enrichment; Instrument system;QUANTITATIVE-ANALYSIS; LIBS; CADMIUM; SAMPLES; LEAD
The enrichment method of heavy metal in water with graphite and aluminum electrode was studied, and combined with plasma restraint device for improving the sensitivity of detection and reducing the limit of detection (LOD) of elements. For aluminum electrode enrichment, the LODs of Cd, Pb and Ni can be as low as several ppb. For graphite enrichment, the measurement time can be less than 3 min. The results showed that the graphite enrichment and aluminum electrode enrichment method can effectively improve the LIBS detection ability. The graphite enrichment method combined with plasma spatial confinement is more suitable for on-line monitoring of industrial waste water, the aluminum electrode enrichment method can be used for trace heavy metal detection in water. A LIBS method and device for soil heavy metals analysis was also developed, and a mobile LIBS system was tested in outfield. The measurement results deduced from LIES and ICP-MS had a good consistency. The results provided an important application support for rapid and on-site monitoring of heavy metals in soil. (C) 2017 Elsevier B.V. All rights reserved.
Laser-induced breakdown spectroscopy; LIBS; Variable angle; Incidence angle; Collection angle; Partial least-squares analysis; PLS;
Laser-induced breakdown spectroscopy has become a popular tool for rapid elemental analysis of geological materials. However, quantitative applications of LIBS are plagued by variability in collected spectra that cannot be attributed to differences in geochemical composition. Even under ideal laboratory conditions, variability in LIBS spectra creates a host of difficulties for quantitative analysis. This is only exacerbated during field work, when both the laser-sample distance and the angle of ablation/collection are constantly changing. A primary goal of this study is to use empirical evidence to provide a more accurate assessment of uncertainty in LIBS-derived element predictions. We hope to provide practical guidance regarding the angles of ablation and collection that can be tolerated without substantially increasing prediction uncertainty beyond that which already exists under ideal laboratory conditions. Spectra were collected from ten geochemically diverse samples at angles of ablation and collection ranging from 0 degrees to +/- 60 degrees. Ablation and collection angles were changed independently and simultaneously in order to isolate spectral changes caused by differences in ablation angle from those due to differences in collection angle. Most of the variability in atomic and continuum spectra is attributed to changes in the ablation angle, rather than the collection angle. At higher angles, the irradiance of the laser beam is lower and produces smaller, possibly less dense plasmas. Simultaneous changes in the collection angle do not appear to affect the collected spectra, possibly because smaller plasmas are still within the viewing area of the collection optics, even though this area is reduced at higher collection angles. A key observation is that changes in the magnitude of atomic and total emission are <5% and 10%, respectively, in spectra collected with the configuration that most closely resembles field measurements (W) at angles <20 degrees. In addition, variability in atomic and continuum emission is strongly dependent upon sample composition. Denser, more Fe/Mg-rich rocks exhibited much less variability with changes in ablation and collection angles than Si-rich felsic rocks. Elemental compositions of our variable angle data that were predicted using a much larger but conventionally-collected calibration suite show that accuracy generally suffers when the incidence and collection angles are high. Prediction accuracy (for measurements acquired with varying collection and ablation angles) varies from +/- 1.28-1.86 wt% for Al2O3, +/- 1.25-1.66% wt for CaO, +/- 1.90-2.21 wt% for Fe2O3T, +/- 0.76-0.94 wt% for K2O, +/- 2.85-3.61 wt% MgO, +/- 0.15-0.17 wt% for MnO, +/- 0.68-0.78 wt% for Na2O, +/- 0.33-0.42 wt% for TiO2, and +/- 2.94-4.34 wt% SiO2. The ChemCam team is using lab data acquired under normal incidence and collection angles to predict the compositions of Mars targets at varying angles. Thus, the increased errors noted in this study for high incidence angle measurements are likely similar to additional, unacknowledged errors on ChemCam results for non-normal targets analyzed on Mars. Optimal quantitative analysis of LIBS spectra must include some knowledge of the angle of ablation and collection so the approximate increase in uncertainty introduced by a departure from normal angles can be accurately reported. (C) 2017 Elsevier B.V. All rights reserved.
Libs; Soil analysis; Practical powder sample holder; Quantitative powder analysis;ATOMIC EMISSION-SPECTROMETRY; SPECTROCHEMICAL ANALYSIS; PLASMA; LIBS; ABLATION; MATRIX; METALS; PB
A practical alternative of sample preparation technique is proposed for direct powder analysis using laser-induced breakdown spectroscopy (LIBS) instead of the commonly adopted treatment of pelletizing the powder. The resulted pellet is known to suffer from reduced sensitivity of emission. Besides, it may also give rise to interfering effect from the binder emission. We introduce in this report a more practical technique of using a subtarget supported micro mesh (SSMM) powder sample holder. The LIBS spectrum of standard soil powder measured with 13 mJ 1064 nm Nd:YAG laser in 0.65 kPa ambient air is shown to exhibit the sharp emission lines of all the major elements in the sample. A comparison with the emission spectra measured from the pelletized powder, the spectrum obtained using the SSMM sample holder shows distinctly superior spectral quality marked by the absence of matrix effect found in pelletized powder samples, and the much stronger intensity due to the more effective shock wave plasma induced thermal excitation process produced by the hard subtarget in the sample holder. Repeating the measurement on a number of the standard soil samples of various Pb contents is shown to yield a linear calibration line with practically zero intercept and a detection limit of less than 10 ppm. We have thus demonstrated the viability of the proposed powder sample holder for the development of practical and quantitative powder analysis in the field. (C) 2017 Elsevier B.V. All rights reserved.
Fan, Z. W. ; Li, X. ; Lian, F. Q. ; Lin, W. R. ; Liu, Y. ; Mo, Z. Q. ; Nie, S. Z. ; Wang, P. ; Xiao, H. ; Zhang, H. B. ; Zhong, Q. X.
LIBS instrument design; Liquid steel analysis; On-line process monitoring; Vacuum alloys production; Laser-induced breakdownspectroscopy;LIBS; STEEL
Laser-induced breakdown spectroscopy (LIBS) utilizing an echelle spectrograph-ICCD system is employed for online analysis of elements concentration in a vacuum induction melting workshop. Active temperature stabilization of echelle spectrometer is implemented specially for industrial environment applications. The measurement precision is further improved by monitoring laser parameters, such as pulse energy, spatial and temporal profiles, in real time, and post-selecting laser pulses with specific pulse energies. Experimental results show that major components of nickel-based alloys are stable, and can be well detected. By using internal standard method, calibration curves for chromium and aluminum are obtained for quantitative determination, with determination coefficient (relative standard deviation) to be 0.9559 (<22%) and 0.9723 (<2.8%), respectively. (C) 2017 Elsevier B.V. All rights reserved.
LIBS; Diffuse reflectance; Portable instrument; Hybrid spectrometer; Pigments;IN-SITU; CULTURAL-HERITAGE; MULTITECHNIQUE APPROACH; WALL PAINTINGS; RAMAN ANALYSIS; LIBS; FIBER; ART; IDENTIFICATION; FLUORESCENCE
A novel, portable spectrometer, combining two analytical techniques, laser-induced breakdown spectroscopy (LIBS) and diffuse reflectance spectroscopy, was developed with the aim to provide an enhanced instrumental and methodological approach with regard to the analysis of pigments in objects of cultural heritage. Technical details about the hybrid spectrometer and its operation are presented and examples are given relevant to the analysis of paint materials. Both LIBS and diffuse reflectance spectra in the visible and part of the near infrared, corresponding to several neat mineral pigment samples, were recorded and the complementary information was used to effectively distinguish different types of pigments even if they had similar colour or elemental composition. The spectrometer was also employed in the analysis of different paints on the surface of an ancient pottery sherd demonstrating the capabilities of the proposed hybrid diagnostic approach. Despite its instrumental simplicity and compact size, the spectrometer is capable of supporting analytical campaigns relevant to archaeological, historical or art historical investigations, particularly when quick data acquisition is required in the context of surveys of large numbers of objects and samples. (C) 2017 Elsevier B.V. All rights reserved.
Laser induced breakdown spectroscopy; Explosive detection; Principal component analysis; Multivariate analysis;LIBS; CLASSIFICATION
We report the 'standoff detection' of explosives at 1 m in laboratory conditions, for the first time in India, using Laser Induced Breakdown Spectroscopycombined with multivariate analysis. The spectra of a set of five secondary explosives were recorded at a distance of 1 m from the focusing as well as collection optics. The plasma characteristics viz., plasma temperature and electron density were estimated from Boltzmann statistics and Stark broadening respectively. Plasma temperature was estimated to be of the order of (10.9 +/- 2.1) x 10(3) K and electron density of (3.9 +/- 0.5) x 10(16) cm(-3). Using a ratiometric approach, C/H and H/O ratios showed a good correlation with the actual stoichiometric ratios and a partial identification success could be achieved. Finally employing principle component analysis, an excellent classification could be attained.
COD; LIBS; Prediction model; Measurement;WASTE-WATER
Using spectroscopy sensing technology to measure water COD is the trend of development of modern environmental monitoring. Compared to the traditional chemical analysis is has the benefits of online continuous detection of environmental water samples for real-time monitoring of water COD. This paper collected real water samples, using laser-induced breakdown spectroscopy (LIBS) to obtain water samples of spectral data. Establish water sample COD quantitative prediction model combining Partial Least Squares regression (PLS) by different spectral pretreatment method, then quantitative prediction of LIES spectrum measurement method of water COD and the relevant model parameters were analyzed. Found that the baseline correction superimposed S-Golay derivative partial least-squares model had better prediction results. The determination coefficient of calibration samples were 0. 995 8, while the determination coefficient of prediction were 0. 975 3, with RMSEC of 4. 438 7 and RMSEP of 9. 733 9. The experimental results showed that spectrum sensing technology can be used in the actual environment of water COD quantitative predictive analysis, laid the theoretical foundation for the development of portable water testing equipment.
Laser-induced breakdown spectroscopy; Plastic; Partial least squares; Classification;IDENTIFICATION; LIBS; DISCRIMINATION; POLYMERS
The traditional ways of waste plastics processing mainly use the burning landfill, which lead to environmental pollution and the waste of resources. Waste plastic recycling is very important on the circulation economy and the sustainable development. The traditional instruments have some shortcomings in plastic classification, such as lower precision, higher cost, the influence of the sample color and a serious threat to operating personnel's health. Laser inducedbreakdown spectroscopy has many advantages, such as simultaneous multielement detection of elements, free from sample preparation, rapid and real-time analysis, slight damages to sample and no impact on the sample color. The method of Chemometrics combined with LIBS technique is applied to the plastic, which improves the accuracy of plastic classification. But at present, the classification has many problems, such as more parameters and the poor universality. Using on a self built LIBS instrument, we can study the laser energy, delay time, integration time and the angle of the optical fiber, which can achieve a better experiment condition. With the experimental platform, we analyze the 2 200 sample points and choose the partial least squares to analyze the spectral data. In order to achieve the correlation between the sample label and the data, we discuss the better ratio of the training set and validation set. The experimental results show that replacing the interference spectra, classification accuracy of all 11 plastic is increased to 100%, while the validation set's accuracy is only 99.8% and the test set is 99.09% without replacing the interference spectra. It can be seen that the laser induced breakdown spectroscopy combined with partial least squares method can be successfully used for the plastic sample classification.
laser-induced breakdown spectroscopy; fireworks; elemental analysis; multivariate analysis; environmental hazards;LANTERN FESTIVAL; AIR-QUALITY; REGRESSION; PARTICLES; EVENTS; TAIWAN; COINS
Different types of fireworks are analyzed using the laser-induced breakdown spectroscopy (LIBS) technique. The system employed for spectral acquisition consists of a Nd:YAG laser (532 nm, FWHM = 4 ns) and an Andor Mechelle ME 5000 echelle spectrometer. The presence of Ba, Ca, Mg, Fe, Na, Sr, Si, and Al is identified in the LIBS spectra of different fireworks. These elements can mix easily into the surroundings and thus pollute the environment. In combination with LIBS, multivariate statistical methods, such as principal component analysis and partial least square discriminant analysis, are employed for qualitative classification, regression, and prediction purposes. These methods show good applicability for the classification and prediction of a large data set.
Benites, V. M. ; Marangoni, B. S. ; Milori, D. M. B. P. ; Nicolodelli, G. ; Romano, R. A. ; Villas-Boas, P. R.
laser-induced breakdown spectroscopy; phosphate rocks; organomineral fertilizers; principal components analysis; partial least squares regression;ELEMENTAL ANALYSIS; PLANT MATERIALS; SOIL; CHEMOMETRICS
A number of phosphate rocks and organomineral P fertilizers was analyzed comparatively by laser-induced breakdown spectroscopy (LIBS) in both single- and double-pulse modes associated with two chemometric methods, i.e., principal components analysis (PCA) and partial least squares regression (PLSR). PCA was demonstrated to be a valuable method for the identification of spectral differences between similar samples with only minor compositional differences. The raw and normalized LIBS spectra were able to provide effective identification and discrimination at a 95% confidence level and in good agreement with the reference concentrations. Results obtained confirm the promising potential of LIBS for the rapid classification of P fertilizers in situ.
Laser-induced breakdown spectroscopy; X-ray fluorescence; Reflectance spectroscopy; Data fusion; Mineral interpretation; Partial least squares;INDUCED BREAKDOWN SPECTROSCOPY; QUANTITATIVE MINERALOGY; RAMAN-SPECTROSCOPY; WESTERN-AUSTRALIA; WAVELENGTH; DEPOSIT
This article is extension of the earlier work (Khajehzadeh et al., 2016), where quantitative mineralogical information of slurry samples was achieved using an on-stream LIES analyzer. Despite the great advances in the analytical methods and laser-based measurement techniques, the industrial developers are still demanding novel ideas enabling differentiation between minerals having similar elemental contents such as hematite and magnetite or silicon-bearing minerals such as quartz and other mixed silica minerals since they have different flotation properties. The available analytical techniques for LIES spectral analysis (including the earlier work of this research) could not distinguish between such minerals with identical elemental contents. This work at first presents data fusion of LIES and reflectance spectroscopy and then discusses the data fusion of reflectance spectroscopy and X-ray fluorescence (XRF) measurement techniques operating on the same slurry samples. The results will show that such data integrations enable on-stream and quantitative identification of slurry mineral contents specially for hematite, magnetite, quartz and ferrorichterite which are important minerals in iron ore beneficiation.
LASER-INDUCED BREAKDOWN; PLASMA-MASS SPECTROMETRY; RESOLUTION CONTINUUM SOURCE; PARTICLE ICP-MS; RAY-FLUORESCENCE SPECTROMETRY; MULTI-ANALYTICAL APPROACH; OPTICAL-EMISSION SPECTROSCOPY; LI-ION BATTERIES; ELECTRON-PARAMAGNETIC-RESONANCE; ELEMENTAL IMPURITIES ANALYSIS
This ASU review focuses on developments in applications of atomic spectrometry to the characterisation of metals, chemicals and materials. It is difficult to identify research trends solely from an annual review of the literature, but a certain perspective can be obtained from examining the developments described in recent years in this ASU review series. It is, for example, evident that there has been a decline in truly novel applications for the analysis of chemicals, perhaps indicative of the fact that, for most sample types, there is now an abundance of methods available in the literature. Those papers that have appeared in the year under review have either focused on specific problems not yet fully addressed (e.g. determination of Si in gasoline) or on incremental development of well-established approaches to sample preparation or measurement. Nevertheless, there has been a very noticeable increase in activity in relation to publication of methods for the characterisation of pharmaceuticals. This is directly linked to changes in the US Pharmacopeia requirements for registration of pharmaceuticals for human use that require assessments to be made for trace element content. Laser-induced breakdown spectrometry is becoming widely employed for applications involving the characterisation of a wide variety of metals, materials and other solid sample types. Efforts are being made to overcome the perceived weaknesses of the technique, such as lack of sensitivity, elemental fractionation, accuracy and/or precision. Advances have been made, for example, using dual-pulse lasers to improve sensitivity, or by employing chemometrics methods with full spectrum data to improve the robustness of calibration. Many of these reported LIBS developments draw from, and have relevance for, applications involving LA-ICP-MS, which continues to be a popular means of generating highly sensitive lateral and depth profiling and bulk compositional information for a wide range of materials and solids. The use of field portable instrumentation for in situ analysis continues grow, with LIBS and XRF techniques amongst those most frequently cited. The development of such instrumentation has had a substantial impact in the examination of cultural heritage artefacts, especially in relation to paintings, wall murals and other objects of unique historical value. The latter area of application has also seen continued use of combinations of surface (SIMS, XPS, SEM-EDS, PIXE, GD and laserablation methods) and bulk (ICP-OES, ICP-MS, AAS, XRF) analysis techniques to reveal details of objects that would not otherwise be identified (for example preparatory sketches hidden under original works of art or materials provenance). This trend towards using a multi-technique based approach has also been apparent in the characterisation of multi-layer or heterogeneous organic and inorganic materials and metals. Finally, methods for the analysis of nanoparticles and nanostructures have been reported, based primarily on single particle (SP)-ICP-MS and flow field flow fractionation (A4F). The investigation of methods of drift correction, the use of flow injection and isotope dilution methodologies in combination with SP-ICP-MS are indicative of the further development of this field.
Morsy, M. A.
Plasma; Laser; EPR; DP-LIBS; Mn-analysis; PVA polymer;INDUCED PLASMA SPECTROSCOPY; INDUCED BREAKDOWN SPECTROSCOPY; SINGLE; EPR; IDENTIFICATION; ULTRAVIOLET; CRYSTALS; LIBS
Series of manganese-co-precipitated poly (vinyl alcohol) (PVA) polymer were quantitatively and qualitatively analyzed using laser ablation system (LAS) based on double-pulse laser induced breakdown spectroscopy (DP-LIBS) and electron paramagnetic resonance (EPR) spectroscopy. The collinear nanosecond laser beams of 266 and 1064 nm were optimized to focus on the surface of the PVA polymer target. Both laser beams were employed to estimate the natural properties of the excited Mn-PVA plasma, such as electron number density (Ne), electron temperature (T-e), and Mn concentration. Individual transition lines of manganese (Mn), carbon (C), lithium (Li), hydrogen (H) and oxygen (0) atoms are identified based on the NIST spectral database. The results show better responses with DP-LIBS than the single-pulse laser induced breakdown spectroscopy (SP-LIBS). On the other hand, the EPR investigation shows characteristic broad peak of Mn-nano-particles (Mn-NPs) in the range of quantum dots of superparamagnetic materials. The line width (peak-to-peak, triangle H-pp) and g-value of the observed Mn-EPR peak are similar to 20 mT and 2.0046, respectively. The intensities of Mn-emission line at a wavelength 403.07 nm and the Mn-EPR absorption peak were used to accurate quantify the Mn-content in the polymer matrix. The results produce linear trends within the studied concentration range with regression coefficient (R-2) value of similar to 0.99, and limit of detection (LOD) of 0.026 mol.% and 0.016 mol.%, respectively. The LOD values are at a fold change of about -0.2 of the studied lowest mol.%. The proposed protocols of trace element detection are of significant advantage and can be applied to the other metal analysis. (C) 2017 Elsevier Ltd. All rights reserved.
Tablet physical-mechanical properties; Density; Porosity; Tablet breaking force; Pharmacopeial methods; Emerging technologies;NEAR-INFRARED SPECTROSCOPY; INDUCED BREAKDOWN SPECTROSCOPY; LIGHT-INDUCED FLUORESCENCE; BREAKING STRENGTH TESTERS; AMYLOSE STARCH TABLETS; X-RAY MICROTOMOGRAPHY; AIR-COUPLED ACOUSTICS; PHARMACEUTICAL TABLETS; RAMAN-SPECTROSCOPY; COATING THICKNESS
The density, porosity, breaking force, viscoelastic properties, and the presence or absence of any structural defects or irregularities are important physical-mechanical quality attributes of popular solid dosage forms like tablets. The irregularities associated with these attributes may influence the drug product functionality. Thus, an accurate and efficient characterization of these properties is critical for successful development and manufacturing of a robust tablets. These properties are mainly analyzed and monitored with traditional pharmacopeial and non-pharmacopeial methods. Such methods are associated with several challenges such as lack of spatial resolution, efficiency, or sample-sparing attributes. Recent advances in technology, design, instrumentation, and software have led to the emergence of newer techniques for non-invasive characterization of physical-mechanical properties of tablets. These techniques include near infrared spectroscopy, Raman spectroscopy, X-ray microtomography, nuclear magnetic resonance (NMR) imaging, terahertz pulsed imaging, laser-induced breakdown spectroscopy, and various acoustic-and thermal-based techniques. Such state-of-the-art techniques are currently applied at various stages of development and manufacturing of tablets at industrial scale. Each technique has specific advantages or challenges with respect to operational efficiency and cost, compared to traditional analytical methods. Currently, most of these techniques are used as secondary analytical tools to support the traditional methods in characterizing or monitoring tablet quality attributes. Therefore, further development in the instrumentation and software, and studies on the applications are necessary for their adoption in routine analysis and monitoring of tablet physical-mechanical properties.
Brown, E. E. ; Hommerich, U. ; Jin, F. ; Patel, S. ; Ramer, E. D. ; Samuels, A. C. ; Swaminathan, S. R. ; Trivedi, S. B.
QUANTITATIVE-ANALYSIS; ENERGETIC MATERIALS; EMISSIONS; LIBS; WAVE
This is the first report of a simultaneous ultraviolet/visible/NIR and longwave infrared laser-induced breakdown spectroscopy (UVN + LWIR LIBS) measurement. In our attempt to study the feasibility of combining the newly developed rapid LWIR LIBS linear array detection system to existing rapid analytical techniques for a wide range of chemical analysis applications, two different solid pharmaceutical tablets, Tylenol arthritis pain and Bufferin, were studied using both a recently designed simultaneous UVN + LWIR LIBS detection system and a fast AOTF NIR (1200 to 2200 nm) spectrometer. Every simultaneous UVN + LWIR LIBS emission spectrum in this work was initiated by one single laser pulse-induced micro-plasma in the ambient air atmosphere. Distinct atomic and molecular LIBS emission signatures of the target compounds measured simultaneously in UVN (200 to 1100 nm) and LWIR (5.6 to 10 mu m) spectral regions are readily detected and identified without the need to employ complex data processing. In depth profiling studies of these two pharmaceutical tablets without any sample preparation, one can easily monitor the transition of the dominant LWIR emission signatures from coating ingredients gradually to the pharmaceutical ingredients underneath the coating. The observed LWIR LIBS emission signatures provide complementary molecular information to the UVN LIBS signatures, thus adding robustness to identification procedures. LIBS techniques are more surface specific while NIR spectroscopy has the capability to probe more bulk materials with its greater penetration depth. Both UVN + LWIR LIBS and NIR absorption spectroscopyhave shown the capabilities of acquiring useful target analyte spectral signatures in comparable short time scales. The addition of a rapid LWIR spectroscopic probe to these widely used optical analytical methods, such as NIR spectroscopy and UVN LIBS, may greatly enhance the capability and accuracy of the combined system for a comprehensive analysis. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
SPATIAL CONFINEMENT; BEAM GEOMETRY; SPECTROSCOPY; IMPROVEMENT; EXPOSURE
The inevitable problems in laser induced breakdown spectroscopy are matrix effect and statistical fluctuation of the spectral signal, which can be partly avoided by utilizing a proper confined unit. The dependences of spectral signal enhancement on relative permittivity were studied by varying materials to confine the plasma, which include polytetrafluoroethylene( PTFE), nylon/dacron, silicagel, and nitrile-butadiene rubber (NBR) with the relative permittivity 2.2, similar to 3.3, 3.6, 8 similar to 13, 15 similar to 22. We found that higher relative permittivity rings induce stronger enhancement ability, which restricts the energy dissipation of plasma better and due to the reflected electromagnetic wave from the wall of different materials, the electromagnetic field of plasma can be well confined and makes the distribution of plasma more orderly. The spectral intensities of the characteristic lines Si I 243.5 nm and Si I 263.1 nm increased approximately 2 times with relative permittivity values from 2.2 to similar to 20. The size dependent enhancement of PTFE was further checked and the maximum gain was realized by using a confinement ring with a diameter size of 5 mm and a height of 3 mm (D5mmH3mm), and the rings with D2mmH1mm and D3mmH2mm also show higher enhancement factor. In view of peak shift, peak lost and accidental peaks in the obtained spectra were properly treated in data progressing; the spectral fluctuation decreased drastically for various materials with different relative permittivities as confined units, which means the core of plasma is stabilized, attributing to the confinement effect. Furthermore, the quantitative analysis in coal shows wonderful results-the prediction fitting coefficient R-2 reaches 0.98 for ash and 0.99 for both volatile and carbon. (C) 2017 Optical Society of America under the terms of the OSA Open Access Publishing Agreement
laser-induced breakdown spectroscopy; ageing layer depth; silicone polymer surface;SPECTROMETRY; LIBS
Silicone rubber composite materials have been widely used in high voltage transmission lines for anti-pollution flashover. The aging surface of silicone rubber materials decreases service properties, causing loss of the anti-pollution ability. In this paper, as an analysis method requiring no sample preparation that is able to be conducted on site and suitable for nearly all types of materials, laser-induced breakdown spectroscopy (LIBS) was used for the analysis of newly prepared and aging (out of service) silicone rubber composites. With scanning electron microscopy (SEM) and hydrophobicity test, LIBS was proven to be nearly non-destructive for silicone rubber. Under the same LIBS testing parameters, a linear relationship was observed between ablation depth and laserpulses number. With the emission spectra, all types of elements and their distribution in samples along the depth direction from the surface to the inner part were acquired and verified with EDS results. This research showed that LIBS was suitable to detect the aging layer depth and element distribution of the silicone rubber surface.
DATA NORMALIZATION; DOMINANT FACTOR; CLASSIFICATION; MODEL; LIBS; REGRESSION; SAMPLES; STEEL; RAMAN; NIR
Laser-induced breakdown spectroscopy (LIBS) as a rapid and green method was used to detect heavy metals Cr and Pb in pork contaminated in the lab. The laser-induced plasma was generated by a Q-switched Nd:YAG laser, and the LIBS signal was collected by a spectrometer with a charge-coupled device detector. The traditional calibration curves (CC) and multivariate partial least squares (PLS) algorithm were applied and compared to validate the accuracy in predicting the content of heavy metals in samples. The results demonstrated that the correlation coefficient of CC is poor by the classical univariate calibration method, so the univariate calibration analysis cannot effectively serve the quantitative purpose in analyzing heavy metals' residue in pork with a complex matrix. The analysis accuracy was improved effectively by the PLS method, and the correlation coefficient is 0.9894 for Cr and 0.9908 for Pb. The concentration of Cr and Pb in samples from a prediction set was obtained using the PLS calibration method, and the average relative errors for the 21 samples in the prediction set are lower than 6.53% and 7.82% for Cr and Pb, respectively. The investigated results display that the matrix effect would be reduced effectively during the quantitative analysis of pork by a LIBS-combined PLS model, and the predictive accuracy would be improved greatly compared to traditional univariate analysis. (C) 2017 Optical Society of America
CHEMICAL-ANALYSIS; PULSE; PLASMA; PRESSURES; SEAWATER; WATER
The exploitation and research of deep-sea hydrothermal vent has been an issue of great interest in ocean research in recent years. Laser-induced breakdownspectroscopy (LIBS) has great potential for ocean application due to the capabilities of stand-off, multiphase, and multielement analysis. In this work, a newly developed compact 4000 m rated LIBS system (LIBSea) is introduced with preliminary results of sea trials. The underwater system consists of an Nd:YAG single-pulsed laser operating at 1064 nm, an optical fiber spectrometer, an optics module, and an electronic controller module. The whole system is housed in an L800 mm x Phi 258 mm pressure housing with an optical window on the end cap. It was deployed on the remote operated vehicle Faxian on the research vessel Kexue, and in June 2015 was successfully applied for hydrothermal field measurements at the Manus area. The obtained results are shown that the LIBS system is capable of detecting elements Li, Na, K, Ca, and Mg in the hydrothermal area. Profiles of LIBS signals of elements K and Ca have also been obtained during the sea trial. The results show that the K emission line is gradually broadened with depth from sea surface to sea floor (1800 m or so); the K intensity shows a hump shape with maximum value at about 1050 m. The Ca emission line is rapidly broadened below 400 m and slowly narrowed to the sea floor; the Ca intensity shows no obvious change below 400 m and increases continuously to sea floor. A very interesting finding is that the small fluctuations of intensity profile curve of Ca show a degree of correlation with seawater temperature change. The sea trial results prove the performance of LIBSea. After further optimization, it is hoped to apply the LIBS system to the in situ mineral deposits and hydrothermal vent fluid detection in deep sea. (C) 2017 Optical Society of America
Amdaoud, M. ; Clavaguera, S. ; Dewalle, P. ; Fauvet, V. ; Gensdarmes, F. ; Golanski, L. ; Guiot, A. ; Motellier, S. ; Ouf, F. X. ; Pontreau, S. ; Quere, C. ; Roynette, A. ; Tabarant, M.
INDUCED PLASMA SPECTROSCOPY; HEAVY-METAL AEROSOLS; X-RAY-FLUORESCENCE; PARTICULATE MATTER; ELEMENTAL COMPOSITION; NANOMATERIALS; WORKPLACES; APPRAISAL; RELEASE; COBALT
Exposure assessment is a key step in the evaluation of the risk induced by the handling of engineered nanomaterials. It is a very complex task, because several properties of nanoparticles are assumed to have an effect on their hazards. For exposure monitoring at the workplace, real-time onsite measurements are commonly implemented to measure the particles size and number density, whereas the sampled material is subsequently analysed by electron microscopy. A complementary approach would consist in doing onsite chemical analysis of the filter samples, in order to routinely monitor a potential chronic exposure. Laser-induced breakdown spectroscopy (LIBS) has distinctive advantages for this purpose. Therefore, this work aims at evaluating the performances of LIBS to assess the exposure to airborne carbon nanotubes (CNTs) at the workplace. As carbon is a ubiquitous element in the environment, our strategy was to target metal impurities in CNTs, aluminum and iron in our case. Then, we proceeded in three steps. First, we optimized the choice of the filter type to get the lowest detection limit for both elements. Secondly, this filter was used to quantitatively measure deposited CNTs. Eventually, we conducted an onsite measurement campaign in an industrial CNT production plant to evaluate the exposure in a real situation. We demonstrated that we could reach a detection limit for CNTs compliant with the current NIOSH recommendation of 1 mu g m(-3), and that the detected CNTs during the onsite campaign in areas accessible to workers were at an extremely low concentration, several orders of magnitude lower than this recommendation.
INDUCED BREAKDOWN SPECTROSCOPY; SPECTRUM STANDARDIZATION METHOD; PARTIAL LEAST-SQUARES; MICROCHIP LASER; CARBON ANALYSIS; MN; SPECTROMETRY; CONFINEMENT; IMPROVEMENT; REGRESSION
Laser-induced breakdown spectroscopy (LIBS) was named a future superstar. Nevertheless, in the last couple of years, several commercial instruments of LIBS and its different variants have become available on a limited scale due to the confinement of quantitative analysis. In this paper, quantitative analysis of various steel samples using a specially designed handheld mu-LIBS instrument and dominant factor based partial-least squares (PLS) regression with spectral standardization is presented. Average absolute measurement errors of 0.019, 0.039, 0.013 and 0.001% for the elements of Si, Cr, Mn and Ni, respectively, were achieved. The average relative standard deviation (RSD) for these elements was less than 5%. A linear calibration response was obtained for C which is difficult to achieve using traditional PLS and for Cu whose concentration in the samples is very low. The results are better than the results of previous LIBS studies using mu J lasers or portable handheld devices, comparable to those obtained using conventional benchtop LIBS systems and better than those of commercial handheld XRF instruments. The present work presents the best results for steel analysis using portable LIBS systems so far and shows the feasibility of the technology for real industrial applications.
INDEPENDENT COMPONENT ANALYSIS; SUPPORT VECTOR MACHINES; NEURAL-NETWORK WNN; QUANTITATIVE-ANALYSIS; RANDOM FOREST; FLY-ASH; WAVELET-TRANSFORM; UNBURNED CARBON; SIGNAL; MODEL
The classification and identification of coal ash contributes to recycling and reuse of metallurgical waste. This work explores the combination of the laser-induced breakdown spectroscopy (LIBS) technique and independent component analysis-wavelet neural network (ICA-WNN) for the classification analysis of coal ash. A series of coal ash samples were compressed into pellets and prepared for LIBS measurements. At first, principal component analysis (PCA) was used to identify and remove abnormal spectra in order to optimize the training set for the WNN model. And then, ICA was employed to select and optimize input variables for the WNN model. The classification of coal ash was carried out by using the WNN model with optimized model parameters (the number of hidden neurons (NHN), the number of iterations (NI), the learning rate (LR) and the momentum) and input variables optimized by ICA. Under the optimized WNN model parameters, the coal ash samples for test sets were identified and classified by using WNN and artificial neural network (ANN) models, and the WNN model shows a better classification performance. It was confirmed that the LIBS technique coupled with the WNN method is a promising approach to achieve the online analysis and process control of the coal industry.
Guo, L. B. ; Hao, Z. Q. ; Li, J. M. ; Li, X. ; Li, X. Y. ; Lu, Y. F. ; Tang, S. S. ; Yang, P. ; Yang, X. Y. ; Yi, R. X. ; Zeng, X. Y.
IN-SITU; LIBS; STEELS; CLASSIFICATION; EXPLORATION; ELEMENTS; SPECTRA; SAMPLES; SOIL; MN
Stand-off laser-induced breakdown spectroscopy (ST-LIBS) has attracted increasing attention as a valuable method for the remote analysis of materials. In this work, a multi-collector (MC) system combining low cost small lenses imitating the structure and shape of an artificial optical compound eye (AOCE) is presented to enhance the spectral intensity of ST-LIBS. The volume of the MC system is one eighteenth smaller than that of a telescope system and the number of collectors can be flexibly changed according to the requirements. The mechanisms of spectral enhancement are also discussed. In order to illustrate the performance of the MC system, the spectral intensities and the limits of detection (LoDs) of Mn and Cr elements acquired by the telescope system and the MC system were compared at a distance of 2 meters. The results showed that the spectral intensity acquired from the MC system was enhanced by 2.2 times, and the LoDs of Mn and Cr were decreased to 294 mu g g(-1) and 49 mu g g(-1). These results indicate that the MC system has great potential in providing a portable, flexible and effective collection method for remote detection.
RARE-EARTH-ELEMENTS; SPACE EXPLORATION; IRON OBJECTS; STEEL WORKS; ICP-MS; LIBS; SPECTROMETRY; UNIVARIATE; SAMPLES; CURVES
Laser-induced breakdown spectroscopy (LIBS) was used for the analysis of charcoal blast furnace slags. Plasma was generated by an application of a 1064 nm wavelength Nd:YAG laser beam to the surface of pellets created from the slags. The presence of Al, Ca, Fe, K, Mg, Mn, and Si was determined by identifying their characteristic spectral signatures. Multivariate analysis was performed for the quantification of these elements. The predicted LIBS results were found in agreement with the inductively coupled plasma optical emission spectrometry analysis. The limit of detection for Al, Ca, Fe, K, Mg, Mn, and Si was calculated to be 0.10%, 0.22%, 0.02%, 0.01%, 0.01%, 0.005%, and 0.18%, respectively. (C) 2017 Optical Society of America
Spectrum Analysis [E05.1962.867]; Laser-Induced Breakdown-Spectroscopy; Tissues [A10]; Optical Tissue Differentiation and Identification;NORMAL HUMAN ENAMEL; HUMAN TOOTH ENAMEL; LINGUAL NERVE; MINERAL-COMPOSITION; FEEDBACK MECHANISM; PERIPHERAL-NERVES; CHEMICAL-ANALYSIS; LIBS PROSPECTS; SURGICAL LASER; DENTAL-CARIES
Compared to conventional techniques, Laser surgery procedures provide a number of advantages, but may be associated with an increased risk of iatrogenic damage to important anatomical structures. The type of tissue ablated in the focus spot is unknown. Laser-Induced Breakdown-Spectroscopy (LIBS) has the potential to gain information about the type of material that is being ablated by the laser beam. This may form the basis for tissue selective laser surgery. In the present study, 7 different porcine tissues (cortical and cancellous bone, nerve, mucosa, enamel, dentine and pulp) from 6 animals were analyzed for their qualitative and semiquantitative molecular composition using LIBS. The so gathered data was used to first differentiate between the soft-and hard-tissues using a Calcium-Carbon emission based classifier. The tissues were then further classified using emission-ratio based analysis, principal component analysis (PCA) and linear discriminant analysis (LDA). The relatively higher concentration of Calcium in the hard tissues allows for an accurate first differentiation of soft-and hard tissues (100% sensitivity and specificity). The ratio based statistical dif-ferentiation approach yields results in the range from 65% (enamel-dentine pair) to 100% (nerve-pulp, cancellous bone-dentine, cancellous bone-enamel pairs) sensitivity and specificity.
Gerbi, M. E. M. D. ; Harvey, C. M. ; Chan, J. W. ; Ivaldi, J. C. ; Phillips, A. ; Smith, D. ; Smith, Z. J. ; Wachsmann-Hogiu, S.
dental caries; ultra-short lasers; thermal effects; atomic spectroscopy;INDUCED BREAKDOWN SPECTROSCOPY; QUANTITATIVE-ANALYSIS; REPETITION-RATE; TISSUE; FLUORESCENCE; CARIES; LIBS; BONE; IDENTIFICATION; ENAMEL
The goal of this work is to investigate the thermal effects of femtosecond laser (fs-laser) ablation for the removal of carious dental tissue. Additional studies identify different tooth tissues through femtosecond laser induced breakdown spectroscopy (fsLIBS) for the development of a feedback loop that could be utilized during ablation in a clinical setting. Scanning Election Microscope (SEM) images reveal that minimal morphological damages are incurred at repetition rates below the carbonization threshold of each tooth tissue. Thermal studies measure the temperature distribution and temperature decay during laserablation and after laser cessation, and demonstrate that repetition rates at or below 10kHz with a laser fluence of 40 J/cm(2) would inflict minimal thermal damage on the surrounding nerve tissues and provide acceptable clinical removal rates. Spectral analysis of the different tooth tissues is also conducted and differences between the visible wavelength fsLIBS spectra are evident, though more robust classification studies are needed for clinical trans-lation. These results have initiated a set of precautionary recommendations that would enable the clinician to utilize femtosecond laser ablation for the removal of carious lesions while ensuring that the solidity and utility of the tooth remain intact.
First-Year Undergraduate/General; Analytical Chemistry; Atomic Spectroscopy; Lasers; Hands-On Learning/Manipulatives; Laboratory Instruction; Metals;LIBS
This laboratory introduces students to laser-induced breakdown spectroscopy (LIBS) for the analysis of metals in soil and rock samples. LIBS employs a laser-initiated spark to induce electronic excitation of metal atoms. Ensuing atomic emission allows for qualitative and semiquantitative analysis. The students use LIBS to analyze a series of standard samples that contain various elements and construct a table of emission line wavelengths for each element analyzed. Students then identify metals in various soil and rock samples. Students gain valuable experience in qualitative analysis using an important spectroscopic tool, while gaining hands-on experience with a spectrometer employing a high energy laser pulse as an excitation source. The LIBS spectrometer is applicable to upper and lower division chemistry courses and can be used as an effective demonstration tool for students in 5th to 12th grade.
Laser-induced breakdown spectroscopy; Matrix-match standard; Principal component analysis; Heat-treated natural zeolite; Sediment samples;HEAVY-METALS; ELEMENTAL ANALYSIS; LIBS LIMIT; SOILS; SAMPLES; SPECTROMETRY; ALLOYS; TOOL
The dependence of laser-induced breakdown spectroscopy (LIBS) to the matrix of the sample remains an important consideration in performing quantitative analysis. In this study, a new matrix was introduced in the preparation of solid powder calibration curves. Heat-treated natural zeolite and KBr were mixed separately into high purity metal powders to generate calibration curves using a univariate approach. A LIBS technique was used in the detection and quantitative analysis of Cr, Cu and Pb in river sediment samples. The relative percent difference (RPD) was calculated to describe the variability measurements made using ICP/OES and LIBS as well as to evaluate the accuracy of the method. Calculated limits of detection in the matrices prepared were comparable with literature values and ranged from 0.41 to 6.1 ppm. The resulting metal concentrations indicate that the natural zeolite matrix were closer to the reference values compared to the KBr matrix. By employing principal component analysis (PCA), heat treated zeolite was shown as a potential diluent or binder for generating calibration curves and could provide matrix-matched standards in identification of target metals from unknown sediment samples. The natural zeolite appeared to closely simulate the ablation behavior and property of the samples, and it is found to be a potential suitable matrix for the quantitative LIBS analysis of sediments. (C) 2017 Elsevier B.V. All rights reserved.
Laminar premixed methane-air flame; Laser-induced breakdown spectroscopy; Flames structure; Radial distribution;BURNING COAL PARTICLE; POLARIZATION SPECTROSCOPY; ANALYTICAL TOOL; ATOMIC SODIUM; JET FLAME; SPECTROMETRY; OH; TEMPERATURE; SPARK; RATIO
Laser-induced breakdown spectroscopy was evaluated for the analysis of the structure of laminar premixed methane-air flames. Firstly, breakdown threshold pulse energy and plasma energy in different areas of the flame were measured simultaneously, and an approximate linear relation between them was detected. Secondly, a new approach was proposed to qualitatively characterize the flame temperature distributions based on the plasma energy distributions. Finally, combination of the spatial analysis of the spectrum intensity, plasma energy and equivalence ratio, the laminar premixed flames structure was investigated deeply, including the distribution of the flame temperature, the width and distribution of different flame region (e.g. premixed combustion regions, high temperature regions.),as well as the location of the flame front. (C) 2017 Elsevier B.V. All rights reserved.
Laser-induced breakdown spectroscopy (LIBS); Signal enhancement; Microwave assisted; Imaging;SPECTROSCOPY LIBS; PLASMA; ENHANCEMENT; DISCHARGE
This study reports a sensitive spectroscopic method for quantitative elemental detection by manipulating the temporal and spatial parameters of laser-inducedplasma. The method was tested for indium detection in solid samples, in which laser ablation was used to generate a tiny plasma. The lifetime of the laser-induced plasma can be extended to hundreds of microseconds using microwave injection to remobilize the electrons. In this novel method, temporal integrated signal of indium emission was significantly enhanced. Meanwhile, the projected detectable area of the excited indium atoms was also significantly improved using an interference-, instead of diffraction-, based technique, achieved by directly imaging microwave-enhanced plasma through a novel narrow-bandpass filter, exactly centered at the indium emission line. Quantitative laser-induce breakdown spectroscopy was also recorded simultaneously with the new imaging method. The intensities recorded from both methods exhibit very good mutual linear relationship. The detection intensity was improved to 14-folds because of the combined improvements in the plasma lifetime and the area of detection. Crown Copyright (C) 2017 Published by Elsevier B.V. All rights reserved.
LIBS; Thin films; Thickness;
A new laser-induced breakdown spectroscopy (LIES) technique is proposed to measure the thickness of films thinner than the ablation rate. The film thickness dependence of the signal intensity is used as a calibration curve. It is demonstrated that calibration curves are successfully made for thin W films and (Fe, Cr, Ni) mixed-material films produced in a magnetron sputtering device. (C) 2017 Elsevier B.V. All rights reserved.
LIBS; Cigarette brands; Elemental composition; Plasma parameters; LA-TOF-mass spectrometry;TOBACCO; CRYSTAL; SAMPLES; PLASMA
We present qualitative and quantitative analysis of the trace elements present in different brands of tobacco available in Pakistan using laser inducedbreakdown spectroscopy (LIBS) and Laser ablation Time of Flight Mass Spectrometer (LA-TOFMS). The compositional analysis using the calibration free LIBS technique is based on the observed emission spectra of the laser produced plasma plume whereas the elemental composition analysis using IA-TOFMS is based on the mass spectra of the ions produced by laser ablation. The optical emission spectra of these samples contain spectral lines of calcium, magnesium, sodium, potassium, silicon, strontium, barium, lithium and aluminum with varying intensities. The corresponding mass spectra of the elements were detected in LA-TOF-MS with their composition concentration. The analysis of different brands of cigarettes demonstrates that LIBS coupled with a LA-TOF-MS is a powerful technique for the elemental analysis of the trace elements in any solid sample. (C) 2017 Elsevier B.V. All rights reserved.
Femtosecond laser ablation; Laser induced breakdown spectroscopy (LIBS); Spectrochemical imaging; YBa2Cu3O7 (YBCO); Thin film;OPTICAL-EMISSION SPECTROMETRY; MASS-SPECTROMETRY; ABLATION; SURFACE; SAMPLES; LIBS; PULSES; IDENTIFICATION; METALS; DAMAGE
We investigate femtosecond laser-induced breakdown-spectroscopy (fs-LIBS) for the spectrochemical imaging of thin films with high spatial resolution. Chemical images are obtained by recording LIBS spectra at each site of 2D raster-scans across the samples employing one fs-laser pulse per site. The diffraction images of the Echelle spectrometer are binned to reduce the read-out time of the intensified CCD detector and to increase the stability of the emission signals against peak drifts in the echellograms. For copper thin films on glass the intensities of Cu I emission lines and the size of ablation craters vary non-monotonously with the film thickness h(Cu) = 5-500 nm. The emission efficiency, defined as the Cu I line intensity per ablated volume, strongly decreases for films thicker than the optical penetration depth. The Na I line intensity from glass increases exponentially with decreasing Cu film thickness. For yttrium barium copper oxide (YBCO) thin films on MgO various atomic and molecular emission lines of the laser-induced plasma are measured (film thickness h(YBCO) = 200-1000 nm). The obtained element (Y, Ba, Cu, Mg) and molecular (Y-O) fs-LIBS images match the structure of the micro-patterned YBCO films very well. The achieved lateral resolution delta r = 6 mu m is among the best values reported for spectrochemical LIBS imaging. (C) 2017 Elsevier B.V. All rights reserved.
LIBS; Steel analysis; Material identification; Rolling mill; Production control;QUANTITATIVE-ANALYSIS; HIGH-TEMPERATURE; SAMPLES; SPECTROMETRY; LIBS
Laser-induced breakdown spectroscopy (LIBS) is applied for the elemental analysis of steel blooms in a rolling mill. The 2-3 tons steel blooms with superficial scale are transported in a sequence on a roller table to successive processing steps. Laser ablation of the scale and the analysis of the subsurface bulk steel is carried out using the same laser in <50 s during scheduled stop times of the roller table. Up to 14 elements such as Ni, Cr, and Mo are measured for several hundreds of blooms of low and high alloy steel during routine production. The comparison of the measured with the nominal compositions, results in root mean square errors of prediction in the range of 0.01-0.2 m.-%. The rolling sequence is clearly reflected by the LIBS measurement of the individual blooms demonstrating the feasibility for material identification. Identification rates are estimated from computer simulations by permutation of the LIBS measured values and the reference values from the rolling sequence. (C) 2017 The Authors. Published by Elsevier B.V.
Laser-induced breakdown spectroscopy (LIBS); Gold ore; Gold; Silver; Conditional analysis;INSTRUMENTAL NEUTRON-ACTIVATION; RAY-FLUORESCENCE ANALYSIS; LA-ICP-MS; INDUCED PLASMA; QUANTITATIVE-ANALYSIS; PRECIOUS METALS; SULFIDE ORES; SPECTROMETRY; ABLATION; PYRITE
The performance of laser-induced breakdown spectroscopy (LIBS) to identify and quantify gold and silver in ore samples was evaluated. Ores from a gold-producing mine and samples artificially doped with Au and Ag solutions to previously defined concentrations (surrogates) were prepared as 50-mm pellets prior to LIBS analysis. Silver detection and intensity measurement was straightforward for concentrations from 0.4 to 43 mu g/g and from 1.1 to 375 mu/g in ore and surrogate samples, respectively. Au emission lines were not found after ensemble averageor accumulation of 100-single shot LIBS spectra of ore samples containing up to 9.5 mu/g Au. However, the Au signal was present in the spectra of surrogate samples, for which a detection limit of about 0.8 mu g/g was determined. When the number of sampling shots in ore samples increased, various single shot spectra registered Au emission lines. The number of spectra containing Au emission lines increased with the number of single shots. Those results, as well as scanning electron microscopy analysis of ore samples, suggest that the discrete analyte distribution as well as the inherent discrete characteristics associated to LIBS made the presence of gold in the LIBS spark an unlikely occurrence. The particle sampling rates (the percentage of laser pulses expected to sample at least one particle) were estimated for gold concentrations of 1.1 and 10.0 mu/g as 0.04% and 0.32%, respectively. A Monte Carlo simulation indicated that >100 gold-containing particles should be sampled to accurately represent the discrete character of gold in the ore. Sampling 100 such particles requires >10(5) laser pulses over a single pellet. Despite the fact that this rather large number of shots makes difficult to conduct conditional analysis on pellets, for some samples that withstood 5000 shots, gold quantification in ores was successfully achieved at concentrations as low as 1 mu/g. Results are encouraging and illustrate the applicability of LIBS to gold and silver in field semi-quantitative analysis. (C) 2017 Elsevier B.V. All rights reserved.
BUILDING EXPERT-SYSTEMS; FUEL PROPERTIES; SPECTROSCOPY; MODEL
A quiet but interesting trend has been occurring in material analysis, coincident with the rise of artificial intelligence (Al) and so-called ""deep"" machine learning methods. Astute spectroscopists have always known that there is more information in the spectra that they obtain than simply the molecular or atomic peaks that are directly measured. Particularly with methods such as infrared, Raman, and laser-induced breakdown spectroscopy (LIBS), the spectral background contains a wealth of information about the sample, and analytical combinations of the peaks can provide material properties. Traditionally, such analytical combinations of peaks were performed explicitly by analysts, but now information about material properties embedded in the spectra can be derived implicitly by Al and machine learning algorithms. This column introduces these ideas and touches on recent results indicative of what more may be coming in this direction.
PLASMA-MASS SPECTROMETRY; INDUCED BREAKDOWN SPECTROSCOPY; LASER-ABLATION; RESOLUTION; CHEMISTRY; TISSUES; METALS; CU
Elemental imaging is regarded as a valuable approach for a wide application range in modern medicine. Using tandem laser-ablation laser-inducedbreakdown spectroscopy (LA LIBS) coupled to inductively coupled plasma mass spectrometry (ICP-MS), high-sensitivity detection of trace metals can be combined with the possibility of analyzing nonmetallic bulk components of biological samples (for example, carbon, hydrogen, and oxygen). In this work, the applicability of the tandem LA LIBS approach for the laterally resolved elemental analysis of a mouse model tumor sample after administering cytostatic medication is demonstrated. Results show that trace elements can be detected using the LA-ICP-MS domain of the setup while major components of the samples are analyzed simultaneously using LIBS. By expanding the analyte range covered during one analysis, information could be extracted from the data set that is not accessible to either of the stand-alone analysis methods.
Laser-induced breakdown spectroscopy; Proximate analysis of coal; Spectral fitting; Support vector machine;LIBS; SYSTEM
Online accurate proximate analysis of coal is vitally important to the optimization of industrial production and reduction in coal consumption. However, due to the ""matrix effect"" caused by the complex and diverse coal species in China, the measurement accuracy needs to be improved by using laser-inducedbreakdown spectroscopy (LIBS). In our experiment, both the spectral pretreatment method and the calibration model for the conversion of laser induced coal plasma spectra to the coal proximate analysis results were optimized. Experimental results showed that, compared with the traditional method, the proposed single or multiple-peak Lorentzian spectral fitting for spectral line intensity calculation reduced the mean RSD from 12. 1% to 9. 7%. For kernel function parameters optimization, the mean absolute error (MAE) of the particle swarm optimization (PSO) was smaller than that of the grid parameter (Grid) and the genetic algorithm (GA). The root mean square error (RMSEP) of support vector machine (SVM) regression model based on PSO parameter optimization was less than that of partial least squares regression (PLS). By combining the single- or multiple-peak Lorentzian spectral fitting method with the PSO based SVM for regression modeling, the average absolute errors (AAE) of predicted proximate analysis results were certified to be: 1. 37% for coal ash content of 16%similar to 30%, 1. 77% for coal ash content of 30% or more, 0. 65 MJ . kg(-1) for calorific value of 9 similar to 24 MJ . kg(-1), 1. 09% for volatile matter of 20% or less, and 1. 02% for volatile matter of 20% or more.
Long-pulse laser induced plasmas; Life-time of plasma; Relative standard deviation; Limit of detection;
Laser induced breakdown spectroscopy with long-pulse laser(500 mu s) was used to generate plasma of soil sample in air. The spectroscopy emission characteristic of soil plasma was investigated under the low power-density conditions. Intense continuum background could not be detected (402 similar to 409 and 420 similar to 436 nm) and the long-pulse laser induced plasma had a longer overall life time (about 220 similar to 270 mu s), which was different from the dynamic characteristics using nanosecond laser and ultra short pulse laser. Besides, the spectral lines of Pb I 405. 78 nm and Cr I 425. 43 nm appeared at about 210 and 190 mu s. Intensity of Pb 1405. 78 nm and Cr I 425. 43 nm increased as time passed by, reaching to its maximum at 320 and 350 mu s, respectively. The study results showed that increased interaction time between laser and sample contributed to the formation of ""quasi-stable state plasma"". The relative standard deviation was 2. 21%similar to 6. 35% concluded by 8 times repeated experiments, which showed a better stability of soil plasma by using a long-pulse laser. The detection limits of Pb and Cr were 34. 7 and 40. 0 mg . kg(-1), respectively, which was below the trace element thresholds for Class 1 soil used in the environmental quality standard in China. Parameters characterizing a laser-induced plasma were obtained with the temperature of 6612 K and electron density of 3. 7 X 10(17) cm(-3) in the condition of long-pulse laser. Experimental results showed that it was in local thermodynamic equilibrium.
Feng, X. H. ; Guo, Q. Q. ; Hu, J. D. ; Chang, K. K. ; Chen, R. P. ; Ma, L. Z. ; Sun, H. F. ; Wang, S.
Laser-induced breakdown spectroscopy (LIBS); Tobacco leaves; Plasma; Limit of detection (LOD);
The rapid detection and real-time monitoring of plant elements is very important in the field of agriculture. A method using Laser Induced BreakdownSpectroscopy (LIBS) for the determination of the spectroscopy characteristics of Cu in tobacco was evaluated. To perform the calibration curve, several tobacco samples containing Cu arranged from 8. 59 to 156. 35 mu g . g(-1) were prepared. The amount of Cu prepared in laboratory was measured using atomic absorption spectroscopy. Experiments indicated that the characteristic spectrum of Cu at the wavelength of 324. 75 nm was quite clear, and easy to obtain. From the characteristic spectra obtained from Cu-contained samples, the temperature and density of the plasma induced by laser were calculated to be 39 458. 94 K and 0. 74X 10(16), respectively. The fitting curve between the intensity of the spectral lines and the sample concentrations was established with the correlation coefficient (r square) of 0. 98, the mean relative standard deviation (RSD) of 2. 59%, the limit of detection (LOD) of 7. 72 mu g . g(-1) and the spectral signal-noise ratio of 7. 86. The method was successfully applied to predict the Cu amounts in tobacco samples, which has a potential to be used in cigarette production lines and tobacco breeding.
LIBS; Plasma parameter; Quantitative analysis; Qualitative analysis;EMISSION
Laser Induced Breakdown Spectroscopic (LIBS) technique was used to detect calcium and silicon in an unknown sample. In this method plasma was generated by Nd :YAG laser of wavelength 1 064 nm with energy 400 mJ and pulse duration between 5 similar to 10 ns. The method was applied for the qualitative as well as quantitative analysis. In the qualitative analysis, the electron number density (N-e) of plasma containing calcium and silicon is determined showing that N-e of neutral particles is equivalent to 1016 (cm(-3)) whereas for ionized particles it is 10(17) (cm(-3)). Plasma temperature is measured using Boltzmann plot method which must be greater than 10 000 k. Intensity ratio method is used for the quantitative analysis shows various elements in abundance with calcium and silicon in majority.
Laser-induced breakdown spectroscopy; Quantitative analysis; Standard addition method; Curve fitting; Heavy metals;
Quantitative analysis of four heavy metals Pb, Cr, Cu and Cd in soils and solid wastes using independently developed portable system of laser-inducedbreakdown spectroscopy. A Nd: YAG pulse laser with fundamental wavelength of 1 064 nm is used as the excitation source, with the single pulse energy of 100 mJ the pulse width of 6 ns, and the operating frequency 3 Hz. The echelle spectroscopy with high resolution and wide spectral range is used as the spectral separation device, and the intensified charge coupled device GOOD) as the spectral detection device in the experiment, with the detection range of 200 similar to 500 nm and a resolution of 0.08 similar to 0.12 nm. In order to improve the spectral intensity and detection sensitivity, a device of hemisphere spatially bound is used to restrain the plasma and a optical fiber with multi-channel is used collect the signal. The reception angle is 45 degrees. The laserrepetition rate is 2 Hz while the delay is 1.5 mu s, with the gate width of 1.05 ms. Standard addition method is used to effectively solve the quantitative analysis of samples of unknown matrix. The innovation lies in the fact that, a curve fit instead of a straight line fit is used in the standard addition method to quantitative analyze the heavy metals in soils and solid wastes, which effectively improve the measurement results. Especially for the low concentrations of soil samples, linear fitting can not be used in quantitative analysis, in contrast, the correlation coefficient of curve fitting is much higher, more closer to the national standard measurement methods, to meet soil pollution detection. The result of seven soils and solid wastes samples are as follows, line fitting relative error: Pb 1.26%similar to 79.38%, Cr-22. 44%similar to 82.06%, Cu 15.09%similar to 190.50%, Cd 32.76%similar to 167.96%, and curve fitting relative error respectively Pb - 4.19%similar to 11.92%, Cr-38.31%similar to 9.26%, Cu-7.24% similar to 26.86%, Cd-10.52%similar to 12.94%, the average relative error is 10.47%.
Aints, M. ; Grigore, E. ; Hakola, A. ; Jogi, I. ; Kolehmainen, J. ; Kozlova, J. ; Lungu, C. ; Mandar, H. ; Paris, P. ; Piip, K. ; Porosnicu, C. ; Ruset, C. ; Tervqakangas, S.
ITER relevant coatings; Laser induced breakdown spectroscopy; (LIBS) diagnostics; Ablation rate; Surface morphology;TILES; JET
Laser induced breakdown spectroscopy (LIBS) has been applied to study ITER-relevant coatings with different surface morphology and crystallinity. LIBS elemental depth profiles were compared with those obtained by secondary ion mass spectrometry (SIMS). Depending on surface morphology and crystallinity, the laser ablation rate of the coatings changed by an order of magnitude, the highest ablation rate had samples prepared by thermoionic vacuum discharge. The inclusion of aluminum (proxy for beryllium) increased the ablation rate by a factor of >6. In addition, for W-Al coatings the ablation was non-stoichiometric. (C) 2017 Elsevier B.V. All rights reserved.
Laser-induced breakdown spectroscopy; LIBS; safeguards; pyroprocessing; molten salt; cerium; gadolinium;MELT CRYSTALLIZATION; MOLTEN-SALT; STRONTIUM; CESIUM
Pyroprocessing of used nuclear fuel (UNF) has many advantages-including that it is proliferation resistant. However, as part of the process, special nuclear materials accumulate in the electrolyte salt and present material accountability and safeguards concerns. The main motivation of this work was to explore a laser-induced breakdown spectroscopy (LIBS) approach as an online monitoring technique to enhance the material accountability of special nuclear materials in pyroprocessing. In this work, a vacuum extraction method was used to draw the molten salt (CeCl3-GdCl3-LiCl-KCl) up into 4 mm diameter Pyrex tubes where it froze. The salt was then removed and the solid salt was measured using LIBS and inductively coupled plasma mass spectroscopy (ICP-MS). A total of 36 samples were made that varied the CeCl3 and GdCl3 (surrogates for uranium and plutonium, respectively) concentrations from 0.5 wt% to 5 wt%. From these samples, univariate calibration curves for Ce and Gd were generated using peak area and peak intensity methods. For Ce, the Ce 551.1 nm line using the peak area provided the best calibration curve with a limit of detection (LOD) of 0.099 wt% and a root mean squared error of cross-validation (RMSECV) of 0.197 wt%. For Gd, the best curve was generated using the peak intensities of the Gd 564.2 nm line resulting in a LOD of 0.027 wt% and a RMSECV of 0.295 wt%. The RMSECV for the univariate cases were determined using leave-one-out cross-validation. In addition to the univariate calibration curves, partial least squares (PLS) regression was done to develop a calibration model. The PLS models yielded similar results with RMSECV (determined using Venetian blind cross-validation with 17% left out per split) values of 0.30 wt% and 0.29 wt% for Ce and Gd, respectively. This work has shown that solid pyroprocessing salt can be qualitatively and quantitatively monitored using LIBS. This work has the potential of significantly enhancing the material monitoring and safeguards of special nuclear materials in pyroprocessing.
Laser-induced breakdown spectroscopy (LIBS); laser ablation; stability; monitoring;NEUTRON-ACTIVATION ANALYSIS; SPECTROMETRY; SULFUR; LIBS; ENVIRONMENT; FLUORINE; AEROSOLS; CHLORINE; CONCRETE; COAL
Mastering the change of cement raw materials composition in real time has important significance to timely adjusting the proportion of raw materials and improving the quality of cement products. As a result, a greater need for online chemical sensors is evolving. Laser-induced breakdown spectroscopy (LIBS) possesses many of the characteristics required for such online chemical sensing, and is a promising technique for field measurements in harsh industrial environments. In this work, we developed a LIBS device for online cement raw materials quality monitoring in the way of ejecting gas-powder mixture, and enhanced the measurement stability through approaches including powder concentration of the ejected gas-powder stream stabilization, pulsed laser power stabilization, and optical efficiency enhancement.
IN-SITU ANALYSIS; AEROSOL-PARTICLES; ALUMINUM-ALLOY; STEEL; SPECTROMETRY; CLEANLINESS; ABLATION; EMISSIONS; MELT
In order for metals to meet the demand for critical applications in the automotive, aerospace, and defense industries, tight control over the composition and cleanliness of the metal must be achieved. The use of laser-induced breakdown spectroscopy (LIBS) for applications in metal processing has generated significant interest for its ability to perform quick analyses in situ. The fundamentals of LIBS, current techniques for deployment on molten metal, demonstrated capabilities, and possible avenues for development are reviewed and discussed.
LIBS stratigraphy; Galvanic coatings; Ablation rate; Plasma shielding; Light-plasma interaction; Depth profiling;INDUCED BREAKDOWN SPECTROMETRY; ION-BEAM ANALYSIS; PULSED-LASER DEPOSITION; REDUCED PRESSURE; JEWELRY INDUSTRY; PURE METALS; ABLATION; SPECTROSCOPY; FILMS; THICKNESS
Laser-induced depth profiling was applied to the investigation of galvanised steel sheets as a typical modern multi-layer coating system for environmental corrosion protection. The samples were ablated stepwise by the use of two different wavelengths of a frequency-converted Nd:YAG-laser, 266nm and 532nm, with a pulse duration of tau = 4ns at fluences ranging from F=50 to 250 J cm(-2). The emission light of the resulting plasma was analysed as a function of both penetration depth and elemental spectrum in terms of linear correlation analysis. Elemental depth profiles were calculated and compared to EDX-cross sections of the cut sample. A proven mathematical algorithm designed for the reconstruction of layer structures from distorted emission traces caused by the Gaussian ablation profile can even resolve thin intermediate layers in terms of depth and thickness. The obtained results were compared to a purely thermally controlled ablation model. Thereby light-plasma coupling is suggested to be a possible cause of deviations in the ablation behaviour of Al. The average ablation rate h as a function of fluence F for Ni ranges from 1 to 3.5 mu m/pulse for lambda = 266nm as well as for lambda =532nm. In contrast, the range of h for Al differs from 2 to 4 mu m/pulse for lambda = 532 nm and 4 to 8 mu m/pulse for lambda = 266 nm in the exact same fluence range on the exact same sample. (C) 2016 Elsevier B.V. All rights reserved.
LIBS; Femtosecond; Organic solar cell; Selective ablation; Depth profiling;DEPTH-RESOLVED ANALYSIS; SELECTIVE ABLATION; SOLAR-CELLS; SPECTROMETRY; LIBS; ABSORPTION; COATINGS; SPECTRA; SAMPLES; PULSES
The potential of laser induced breakdown spectroscopy (LIBS) as a non-contact probe, for characterizing organic photovoltaic devices during selective laserscribing, was investigated. Samples from organic solar cells were studied, which consisted of several layers of materials including a top electrode (Al, Mg or Mo), organic layer, bottom electrode (indium tin oxide), silicon nitride barrier layer and substrate layer situated from the top consecutively. The thickness of individual layers varies from 115 to 250 nm. LIBS measurements were performed by use of a 40 femtosecond Ti:Sapphire laser operated at very low pulse energy (<10 micro-joule) to ensure a fine depth-profiling of the very thin layers. Probing a fixed spot on the sample with successive laser pulses, produced plasma emission spectra corresponding to individual laser ablation events. This enabled discrimination of the different layers on the basis of characteristic spectral lines reflecting key elemental constituents of each layer in the organic solar cell structure, demonstrating the potential of LIBS for fast, non-contact characterization of organic photovoltaic coatings. (C) 2016 The Author(s). Published by Elsevier B.V.
Laser-induced breakdown spectroscopy; Silver nanoparticles; Distribution; Root tissues;ARABIDOPSIS-THALIANA; PLANT-SAMPLES; ACCUMULATION; CADMIUM; MATRIX; SIZE
The manuscript presents a procedure for optimal sample preparation and the mapping of the spatial distribution of metal ions and nanoparticles in plant roots using laser-induced breakdown spectroscopy (LIBS) in a double-pulse configuration (DP LIBS) in orthogonal reheating mode. Two Nd:YAG lasers were used; the first one was an ablation laser (UP-266 MACRO, New Wave, USA) with a wavelength of 266 nm, and the second one (Brilliant, Quantel, France), with a fundamental wavelength of 1064 nm, was used to reheat the microplasma. Seedlings of Vicia faba were cultivated for 7 days in CuSO4 or AgNO3 solutions with a concentration of 10 mu mol 1(-1) or in a solution of silver nanoparticles (AgNPs) with a concentration of 10 mu mol 1(-1) of total Ag, and in distilled water as a control. The total contents of the examined metals in the roots after sample mineralization as well as changes.in the concentrations of the metals in the cultivation solutions were monitored by ICP-OES. Root samples embedded in the TissueTek medium and cut into 40 gm thick cross sections using the Cryo-Cut Microtome proved to be best suited for an accurate LIBS analysis with a 50 gm spatial resolution. 2D raster maps of elemental distribution were created for the emission lines of Cu(I) at 324.754 nm and Ag(I) at 328.068 nm. The limits of detection of DP LIES for the root cross sections were estimated to be 4 pg for Cu, 18 pg for Ag, and 3 pg for AgNPs. The results of Ag spatial distribution mapping indicated that unlike Ag+ ions, AgNPs do not penetrate into the inner tissues of Vicia faba roots but stay in their outermost layers. The content of Ag in roots cultivated in the AgNP solution was one order of magnitude lower compared to roots cultivated in the metal ion solutions. The significantly smaller concentration of Ag in root tissues cultivated in the AgNP solution also supports the conclusion that the absorption and uptake of AgNPs by roots of Vicia faba is very slow. LIBS mapping of root sections represents a fast analytical method with sufficient precision and spatial resolution that can provide very important information for researchers, particularly in the fields of plant science and ecotoxicology.
Laser Induced Breakdown Spectroscopy; Milk adulteration; Melamine; Neural networks;NEURAL-NETWORKS; POWDER ADULTERATION; VEGETABLE-OILS; BETA-CAROTENE; DISCRIMINATION; CLASSIFICATION; LYCOPENE; FATS; MS
The present work focuses on the development of a fast and cost effective method based on Laser Induced Breakdown Spectroscopy (LIBS) to the quality control, traceability and detection of adulteration in milk. Two adulteration cases have been studied; a qualitative analysis for the discrimination between different milk blends and quantification of melamine in adulterated toddler milk powder. Principal Component Analysis (PCA) and neural networks (NN) have been used to analyze LIBS spectra obtaining a correct classification rate of 98% with a 100% of robustness. For the quantification of melamine, two methodologies have been developed; univariate analysis using CN emission band and multivariate calibration NN model obtaining correlation coefficient (R-2) values of 0.982 and 0.999 respectively. The results of the use of LIBS technique coupled with chemometric analysis are discussed in terms of its potential use in the food industry to perform the quality control of this dairy product. (C) 2017 Elsevier Ltd. All rights reserved.
SUPPORT VECTOR MACHINES; ELEMENTAL ANALYSIS; IRON-ORES; CLASSIFICATION; SPECTROMETRY; SAMPLES; PLASMA; INDUSTRY; ALLOYS; MODEL
The basicity of sintered ore, which is related to the melting point of the sinter, is vital to ore mining and blastfurnace smelting. Laser-induced breakdownspectroscopy (LIBS) with random forest regression (RFR) has been applied for measuring the basicity of sintered ore, which can be defined by the concentrations of oxides: CaO, SiO2, Al2O3 and MgO. In this work, thirty sintered ore samples are used, of which twenty samples are used for the calibration set to construct the random forest regression (RFR) calibration model for the above-mentioned oxides and ten samples are used for the test set. The characteristic lines of the main components in the sintered ore are identified using the National Institute of Standards and Technology (NIST) database. Two model parameters (the number of decision trees -ntree and the number of random variables - m(try)) of the RFR were optimized by out-of-bag (OOB) error estimation for improving the predictive accuracy of the RFR model. The RFR model was applied to sample measurements and the results were compared with partial least squares regression (PLSR) models. The RFR model has shown better predictive capabilities than the PLSR model. In order to verify the stability of the RFR model, fifty measurements were made and the relative standard deviation (RSD) of the data is between 0.27% and 0.59%. Therefore, LIBS combined with RFR could be a promising method for realtime online, rapid analysis in mining and mineral processing industries.
INDUCED BREAKDOWN SPECTROSCOPY; OPTICAL-EMISSION-SPECTROMETRY; TRACE-ELEMENTS; MICRONUTRIENTS; MEMBRANE; CADMIUM; WATER
A novel calibration method was developed for the determination of macronutrients in suspension fertilizer samples by laser-induced breakdown spectroscopy(LIBS). The fertilizer samples were mixed with 10% m/v polyvinyl alcohol (PVA) and dried for approximately 2 h at 50 degrees C, resulting in a solid polymer film with the immobilized liquid sample. This study describes the use of LIBS and 12 normalization strategies to determine Cu, K, Mg, Mn and Zn as well as As, B, Ca, Cd, Cr, Fe, Na, P and Pb in suspension fertilizers by inductively coupled plasma optical emission spectrometry (ICP OES) and inductively coupled plasma mass spectrometry (ICP-MS) analyses. LIBS equipment parameters were chosen following optimization with a Doehlert design. The results clearly demonstrate a good agreement between the LIBS predicted concentrations and the reference concentrations determined by ICP OES after microwave-assisted acid digestion (AOAC 2006.03 Official Method). Correlations of R-2 = 0.9958, 0.9489, 0.9992, 0.9968 and 0.9809 for Cu, K, Mn, Mg and Zn, respectively, were obtained. Significant levels of potentially toxic elements such as 10 mg L-1 As, 4.0 mg L-1 Cd, 8.0 mg L-1 Cr and 20 mg L-1 Pb were detected after ICP-MS analysis. The results with low standard errors of prediction for LIBS (from 0.02 to 0.06%) indicate that this proposed suspension sample preparation procedure exhibits significant potential for the development and implementation of methods for determining essential nutrients in suspension fertilizers and other samples for which mineralization is difficult.
Dong, L. ; Jia, S. T. ; Ma, W. G. ; Xiao, L. T. ; Yao, S. C. ; Yin, W. B. ; Zhang, L. ; Zhao, Y.
EMISSION-LINES; ALUMINUM; PLASMAS; COAL
A novel self-absorption-free laser-induced breakdown spectroscopy (SAF-LIBS) technique is proposed to directly capture the optically thin spectral line by matching the measured doublet atomic lines intensity ratios with the theoretical one. To realize the experimental SAF-LIBS, the integration time, the fiber collection angle, and the delay time are optimized. The optically thin conditions are validated by comparing the linearity of Boltzmann plots with the traditional self-absorption (SA) correction method and evaluating the SA coefficients. The applicability and limitation of SAF-LIBS on element concentration and laserenergy are also discussed. Univariate quantitative analysis results show that, compared with ordinary LIBS, the average absolute error of aluminum concentration has been reduced by an order of magnitude, which proves that this SAF-LIBS technique is qualified to realize accurate chemical composition measurements. (C) 2017 Optical Society of America
Fe-Ce oxide; Arsenic; Porous soil; Micromodel; Laser-induced breakdown spectroscopy;CONTAMINATED SOILS; POROUS-MEDIA; PORE-SCALE; TRANSPORT; NANOPARTICLES; VISUALIZATION; REMEDIATION; GROUNDWATER; AMENDMENTS
Iron materials have shown great potential to remediate arsenic (As) contaminated sites. It's very important to reveal the reaction process between iron materials and As from the perspective of pore scale, but relevant research was inadequate. In order to directly investigate the migration and As adsorption mechanism of starch-modified Fe-Ce oxide in pore scale, a silicon-based micromodel observation platform was established in this study. The results of Charge coupled Device images showed that the sedimentation surface area of SFC occupied about 57.02% of the large porosity zone, but only 23.27% of the small porosity zone. To further reveal the 3D distribution of Fe and As elements inside the pore network, Laser Induced Breakdown Spectroscopy was introduced. The results revealed that less As was adsorbed as less SFC intruded in the small porosity zone. When the large porosity zone was blocked by SFC, a permeability barrier was created to adsorb As from upstream. This study also explored the effect of particle size reduction on SFC migration, and found it might be a better candidate for more SFC penetrated into small porosity zone. Combined with various high-resolution and sensitivity-detection methodologies, more colloidal migration mechanisms can be investigated using this technology in the future. (C) 2017 Elsevier B.V. All rights reserved.
Bunkin, F. ; Filichkina, V. A. ; Filippov, M. N. ; Grishin, M. Y. ; Pershin, S. M. ; Sdvizhenskii, P. A. ; Stavertiy, A. Y. ; Tretyakov, R. S.
Wear resistant coatings; Tungsten carbide; Elemental profiling; Laser induced breakdown spectroscopy; Energy dispersive X-ray spectroscopy; Laser cladded coating;TUNGSTEN CARBIDE; MICROSTRUCTURAL CHARACTERIZATION; COMPOSITE COATINGS; ABLATION; STEEL; LIBS; WEAR; EXCITATION; PLASMA; PULSES
Multilayer tungsten carbide wear resistant coatings were analyzed by laser induced breakdown spectroscopy (LIBS) and energy dispersive X-ray (EDX) spectroscopy. Coaxial laser cladding technique was utilized to produce tungsten carbide coating deposited on low alloy steel substrate with additional inconel 625 interlayer. EDX and LIBS techniques were used for elemental profiling of major components (Ni, W, C, Fe, etc.) in the coating. A good correlation between EDX and LIBS data was observed while LIBS provided additional information on light element distribution (carbon). A non-uniform distribution of tungsten carbide grains along coating depth was detected by both LIBS and EDX. In contrast, horizontal elemental profiling showed a uniform tungsten carbide particles distribution. Depth elemental profiling by layer by-layer LIBS analysis was demonstrated to be an effective method for studying tungsten carbide grains distribution in wear resistant coating without any sample preparation. (C) 2017 Published by Elsevier B.V.
POLISHING-INDUCED CONTAMINATION; INDUCED DAMAGE THRESHOLD; X-RAY REFLECTION; REFRACTIVE-INDEX; ROUGHNESS; OPTICS; GLASS; MITIGATION; CRACKS; ELLIPSOMETRY
We report on investigations of the spatial variations of contamination, roughness, and index of refraction of classically manufactured polished fused silica surfaces. Therefore, laser-induced breakdown spectroscopy was used to probe surface and subsurface impurities via the detection of aluminum. Measurements at different positions on the surface of the cylindrical fused silica windows evidenced an almost contamination-free center region, whereas a relatively large contamination area was found close to the edge. In-depth measurements verify the presence of aluminum atoms in the bulk until a depth of several tens of microns for the edge region. In addition, atomic force microscopic measurements show that the surface roughness is larger in the center region compared to the edge. Further, the index of refraction increases from the center region towards the edge as measured via ellipsometry. The results indicate a nonuniform impact of the grinding, lapping, and polishing tools on the surface. The findings turn out to be of specific interest for different applications, particularly for the realization of large-scale high-performance coatings. (C) 2017 Optical Society of America
spectroscopy; salt efflorescence; rock art; conservation science;RAMAN-SPECTROSCOPY; CULTURAL-HERITAGE; PAINTINGS; DIAGNOSIS; STONE; WALLS; FTIR
Toca Exu do Jurubeba is part of a set of archaeological sites located in the Serra da Capivara National Park (Piaui, Brazil), a region of great world interest due to its archaeological potential, especially rock art. However, rock art is constantly threatened by both natural and anthropic factors. Among the natural salts efflorescences that are deposited on the painted graphics often even concealing them. The present study consisted of the spectroscopic analysis of different saline efflorescence samples of the Serra da Capivara National Park, using examination techniques (optical microscopy and Scanning Electron Microscopy) and analysis (Fourier Transform Infrared and Laser Induced Breakdown Spectroscopy). The analysis allowed to identify at least four different compositions of the samples as a mixture of hydrated calcium oxalate (CaC2O4 H2O) with kaolinite (Al2SiO3(OH)(4)), gypsum (CaSO4 2H(2)O), tetrahydrate calcium nitrate (Ca(NO3)(2) 4H(2)O) and aluminosilicates in the state of fossilization. The obtained results open the way for the conservation of rock art, initially in the archaeological site under study and can serve as basis for other interventions that may be developed in the region.
Guan, T. ; He, Y. H. ; Chen, X. J. ; Ji, Y. H. ; Li, D. M. ; Liu, S. Y. ; Lu, B. R. ; Shen, Z. Y. ; Zhang, Y. L.
optical demodulation; suspension array; laser-induced breakdown spectroscopy;INDUCED BREAKDOWN SPECTROSCOPY; LASER-INDUCED PLASMA; FLUORESCENCE; IMMUNOASSAYS; MICROBEADS; PROTEINS; LIQUID
A laser-induced breakdown spectroscopy and fluorescence spectroscopy-coupled optical system is reported to demodulate digitally encoded suspension array in fluoroimmunoassay. It takes advantage of the plasma emissions of assembled elemental materials to digitally decode the suspension array, providing a more stable and accurate recognition to target biomolecules. By separating the decoding procedure of suspension array and adsorption quantity calculation of biomolecules into two independent channels, the cross talk between decoding and label signals in traditional methods had been successfully avoided, which promoted the accuracy of both processes and realized more sensitive quantitative detection of target biomolecules. We carried a multiplexed detection of several types of anti-IgG to verify the quantitative analysis performance of the system. A limit of detection of 1.48 x 10(-10) M was achieved, demonstrating the detection sensitivity of the optical demodulation system. (C) The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License.
INDUCED BREAKDOWN SPECTROSCOPY; EMISSION-SPECTROSCOPY; MOLECULAR-EMISSION; ABLATION; AIR; CARBON; ALO; TEMPERATURE; GENERATION; CHEMISTRY
Experimental investigations into the characteristics of laser-induced plasmas indicate that LIBS provides a relatively inexpensive and easily replicable laboratory technique to isolate and measure reactions germane to understanding aspects of high-explosive detonations under controlled conditions. Spectral signatures and derived physical parameters following laser ablation of aluminum, graphite and laser-sparked air are examined as they relate to those observed following detonation of high explosives and as they relate to shocked air. Laser-induced breakdown spectroscopy (LIBS) reliably correlates reactions involving atomic Al and aluminum monoxide (AlO) with respect to both emission spectra and temperatures, as compared to small-and large-scale high-explosive detonations. Atomic Al and AlO resulting from laser ablation and a cited small-scale study, decay within similar to 10(-5) s, roughly 100 times faster than the Al and AlO decay rates (similar to 10(-3) s) observed following the large-scale detonation of an Al-encased explosive. Temperatures and species produced in laser-sparked air are compared to those produced with laser ablated graphite in air. With graphite present, CN is dominant relative to N-2(+). In studies where the height of the ablating laser's focus was altered relative to the surface of the graphite substrate, CN concentration was found to decrease with laser focus below the graphite surface, indicating that laser intensity is a critical factor in the production of CN, via reactive nitrogen. (C) 2017 Author(s).
LIBS quantitative analysis; reduction of matrix effect; internal standard calibration; normalization; correction of self-absorption;PART II; SAMPLES; PARAMETERS
A procedure for matrix effect reduction is proposed to enhance the precision of quantitative analysis of metal alloys using laser-induced breakdownspectroscopy (LIBS). This procedure is based on a number of successive steps in order to correct the signal fluctuations caused by plasma interaction and the matrix effect. The first step is the selection of optimum parameter settings of the detection system, such as laser power, delay time, and focal distance. The second step is the estimation of the absolute or relative values of impurities on the basis of the internal standard calibration. The third step is the analysis of the metal basis of the alloy used as an internal standard, which requires spectrum averaging, whole integral spectrum normalization, and self-absorption correction. Three sets of metal-based alloys (aluminum, steel, and copper) are used in this investigation as reference standards for calibration and validation. Successive improvements of the quality of calibration curves are observed during the proposed procedure.
laser-induced breakdown spectroscopy; soil; magnesium; nonlinear multivariate calibration;RARE-EARTH-ELEMENTS; SAMPLES; LIBS; QUANTIFICATION; DIAGNOSIS; METALS
Laser-induced breakdown spectroscopy (LIBS) coupled with the nonlinear multivariate regression method was applied to analyze magnesium (Mg) contents in soil. The plasma was generated using a 100 mJ Nd:YAG pulsed laser, and the spectra were acquired using a multi-channel spectrometer integrated with a CCD detector. The line at 383.8 nm was selected as the analysis line for Mg. The calibration model between the intensity of characteristic line and the concentration of Mg was constructed. The traditional calibration curve showed that the concentration of Mg was not only related to the line intensity of itself, but also to other elements in soil. The intensity of characteristic lines for Mg (Mg I 383.8 nm), manganese (Mn) (Mn I 403.1 nm), and iron (Fe) (Fe I 407.2 nm) were used as input data for nonlinear multivariate calculation. According to the results of nonlinear regression, the ternary nonlinear regression was the most appropriate of the studied models. A good agreement was observed between the actual concentration provided by inductively coupled plasma mass spectrometry (ICP-MS) and the predicted value obtained using the nonlinear multivariate regression model. The correlation coefficient between predicted concentration and the measured value was 0.987, while the root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) were reduced to 0.017% and 0.014%, respectively. The ratio of the standard deviation of the validation to the RMSEP increased to 8.79, and the relative error was below 1.21% for nine validation samples. This indicated that the multivariate model can obtain better predicted accuracy than the calibration curve. These results also suggest that the LIBS technique is a powerful tool for analyzing the micro-nutrient elements in soil by selecting calibration and validation samples with similar matrix composition.
Bolotov, V. V. ; Bukin, I. O. ; Chekhlenok, A. A. ; Mayor, A. Y. ; Mun, S. A. ; Proschenko, D. Y.
laser spectroscopy; laser sensing; laser induced fluorescence; laser induced breakdown spectroscopy; chlorophyll A; fluorometer; ROV;LIBS; SPECTROMETER; SCIENCE
Laser technologies that are used for the development of sensor elements for Remotely Operated Vehicles (ROVs) are presented, as well as the latest developments in underwater robotics where laser spectroscopy methods are applied to environmental monitoring. A submersible laser spectrometer unit intended for studying Raman scattering and laser-induced fluorescence (LIF) spectra is presented. The spectrometer was developed as an element of an ROV sensor system for remote detection and measurements of organic matter concentrations in sea water and underwater objects. The results of environmental tests of the submersible LIF spectrometer in various marine areas, including the Arctic, are described.
Laser-induced breakdown spectroscopy; Soil; Calibration curve; Chemometrics analysis;LIBS; CALIBRATION
Abundance or deficiency of soil elements is an expression of soil fertility. Rapid detection of elements in soil is a key point of front information acquirement tools in precision agriculture, and it also provides a theoretical basis for pollution prevention of soil heavy metal and sustainable development of agriculture. This research focused on using laser-induced breakdown spectroscopy LIBS) technique combined with calibration curve and chemometrics method to conduct the simultaneous quantitative analysis of multi-elements (Al, Fe, Mg, Ca, Na and K) in soil. First of all, five certified reference materials (CRM) of soil numbered GBW07446, GBW07447, GBW07454, GBW07455, GBW07456 were ablated by a laboratorial LIBS setup in air. 50 LIBS spectra of each type of soil were averaged to reduce the error in experiment process. By integrating the acquired LIBS emission spectra and atomic spectra database from national institute of standards and technology (NIST), analytical spectral lines and corresponding spectral regions were identified. Then, calibration curves of the intensity of a peak and integrated intensity of a peak or several peaks (peak area) coupling with the element content s were fitted. The results indicated that the linear relation from the calibration curves fitted by peak areas and element contents were superior to the calibration curves fitted using intensity of a peak and element contents (except the Fe). Meanwhile, partial least-squares regression (PLSR) was employed to build the quantitative model by using the selected spectral regions and corresponding element contents, which offered a promising result with relatively high RP and showed more advantages than the calibration curve method. The approach revealed that LIES technology combined with chemometrics methods displayed a bight prospect in the field of spectrochemical analysis. The achievements of the research not only provide a guide for detecting soil nutrient spatial distribution and precision fertilization technique, but also lay a theoretical foundation for developing the portable LIBS detector used in the field.
Wear elements in engine oil; Indirect ablation laser induced breakdown spectroscopy; Matrix effect; Calibration curves;LUBRICATING OILS; CRUDE-OIL; QUANTITATIVE-DETERMINATION; MASS-SPECTROMETRY; METALS
Engine oil plays an important role in the engine operation. Elements composition and concentration in engine oil will be changed as the engine operates, which can lead to the deterioration of engine oil, and the engine thereby will be worse. A rapid and effective detection approach for oil performance, therefore, is proposed to prevent further deterioration. Indirect ablation laser induced breakdown spectroscopy (IA-LIES) is a new technology introduced specially for oil samples, which focuses on the indirect ablation of oil samples by metallic plasma with high temperature, improving the detection sensitivity and stability. In this paper, the matrix effect on calibration curves of analytical elements (Mg, Fe and Ni) in different oils was investigated. The results show that the matrix effect is quite small and reasonably negligible. A universal calibration curve can be established for analytical metals in different types of oil, and the linear fitting coefficients are all superior to 0. 99. We used the universal calibration curves to determine the concentrations of Mg, Fe and Ni in mixed oils. The IA-LIES results show a good agreement between the measured and known values. The IA-LIBS is further improved and can promote the detection of engine oil performance, which has important scientific significance for the diagnosis of engine wear.
tungsten ion beam; double-pulse lasers ablation system; laser ablation system; optical Instrumentation;INDUCED BREAKDOWN SPECTROSCOPY; APPLIED ELECTRIC-FIELD; INDUCED PLASMA; SURFACE; SPECTROMETRY; DYNAMICS; WAVELENGTHS; NANOSECOND; PARAMETERS; RADIATION
New tungsten ion source is produced by using single and double-pulse laser ablation system. Combined collinear Nd:YAG laser beams (266+1064 nm) are optimized to focus on the sample in air. Optimization of the experimental parameters is achieved to enhance the signal-to-noise ratio of the emission spectra. The velocity distribution of the emitted plasma cloud is carefully measured. The influences of the potential difference between the bias electrodes, laserwavelength and intensity on the current signal are also studied. The results show that the increase in the tungsten ion velocity under the double-pulse lasers causes the output current signal to increase by about three folds. The electron density and temperature are calculated by using the Stark-broadened line profile of tungsten line and Boltzmann plot method of the upper energy levels, respectively. The signal intensity dependence of the tungsten ion angular distribution is also analyzed. The results indicate that the double-pulse laser ablation configuration is more potent technique for producing more metal ion source deposition, thin film formation, and activated plasma-facing component material.
Cama-Moncunill, X. ; Casado-Gavalda, M. P. ; Cullen, P. J. ; Dixit, Y. ; Markiewicz-Keszycka, M. ; Sullivan, C.
LIBS; Trace-element premixes; Univariate analysis; Multivariate analysis; PLS;SPECTROCHEMICAL ANALYSIS; LIBS; ADULTERATION; COPPER; MILK; BEEF
Infant formula is a human milk substitute generally based upon fortified cow milk components. In order to mimic the composition of breast milk, trace elements such as copper, iron and zinc are usually added in a single operation using a premix. The correct-addition of premixes must be verified to ensure that the target levels in infant formulae are achieved. In this study, a laser-induced breakdown spectroscopy (LIBS) system was assessed as a fast validation tool for trace element premixes. LIBS is a promising emission spectroscopic technique for elemental analysis, which offers real-time analyses, little to no sample preparation and ease of use. LIBS was employed for copper and iron determinations of premix samples ranging approximately from 0 to 120 mg/kg Cu/1640 mg/kg Fe. LIES spectra are affected by several parameters, hindering subsequent quantitative analyses. This work aimed at testing three matrix-matched calibration approaches (simple-linear regression, multi-linear regression and partial least squares regression (PLS)) as means for precision and accuracy enhancement of LIBS quantitative analysis. All calibration models were first developed using a training set and then validated with an independent test set. PLS yielded the best results. For instance, the PLS model for copper provided a coefficient of determination (R-2) of 0.995 and a root mean square error of prediction (RMSEP) of 14 mg/kg. Furthermore, LIBS was employed to penetrate through the samples by repetitively measuring the same spot. Consequently, LIBS spectra can be obtained as a function of sample layers. This information was used to explore whether measuring deeper into the sample could reduce possible surface-contaminant effects and provide better quantifications. (C) 2017 Elsevier B.V. All rights reserved.
Coffee global quality; BGS; Classes discrimination; NIRS; LIBS;NEAR-INFRARED SPECTROSCOPY; MARKER COMPOUNDS; CUP QUALITY; BEANS; DEFECTS
Coffee is an important commodity and a very popular beverage around the world. Its economic value as well as beverage quality are strongly dependent of the quality of beans. The presence of defective beans in coffee blends has caused a negative impact on the beverage Global Quality (GQ) assessed by cupping tests. The main defective beans observed in the productive chain has been those Blacks, Greens and Sours (BGS). Chemical composition of BGS has a damaging impact on beverage GQ That is why analytical tools are needed for monitoring and controlling the GQ in coffee agro-industry. Near Infrared Spectroscopy (NIRS) has been successfully applied for assessment of coffee quality. Another potential technique for direct, clean and fast measurement of coffee GQ is Laser Induced Breakdown Spectroscopy (LIBS). Elements and diatomic molecules commonly present in organic compounds (structure) can be assessed by using LIBS. In this article is reported an evaluation of LIBS for the main interferents of GQ (BGS defects). Results confirm the great potential of LIBS for discriminating good beans from those with BGS defects by using emission lines of C, CN, C-2 and N. Most importantly, some emission lines presented strong linear correlation (r > 0.9) with NIRS absorption bands assigned to proteins, lipids, sugar and carboxylic adds, suggesting LIBS potential to estimate these compounds in unroasted and ground coffee samples. (C) 2017 Elsevier B.V. All rights reserved.
Bernard, J. ; Bockova, J. ; Delepine-Gilon, N. ; Chen, L. ; Chen, Y. P. ; Li, H. ; Martin, S. ; Tang, H. S. ; Veis, P. ; Yan, C. H. ; Yu, J. ; Yu, J. L. ; Zhang, T. L.
Wines; LIBS; Classification; Principal component analysis; Random forest; Matrix effect;LIQUID-LIQUID MICROEXTRACTION; ICP-MS; GEOGRAPHICAL ORIGIN; PROTECTED DESIGNATION; MULTIELEMENT ANALYSIS; SINGLE-PULSE; IDENTIFICATION; SAMPLES; LIBS; METALS
Laser-induced breakdown spectroscopy (LIBS) has been applied to classify French wines according to their production regions. The use of the surface-assisted (or surface-enhanced) sample preparation method enabled a sub-ppm limit of detection (LOD), which led to the detection and identification of at least 22 metal and nonmetal elements in a typical wine sample including majors, minors and traces. An ensemble of 29 bottles of French wines, either red or white wines, from five production regions, Alsace, Bourgogne, Beaujolais, Bordeaux and Languedoc, was analyzed together with a wine from California, considered as an outlier. A non-supervised classification model based on principal component analysis (PCA) was first developed for the classification. The results showed a limited separation power of the model, which however allowed, in a step by step approach, to understand the physical reasons behind each step of sample separation and especially to observe the influence of the matrix effect in the sample classification. A supervised classification model was then developed based on random forest (RF), which is in addition a nonlinear algorithm. The obtained classification results were satisfactory with, when the parameters of the model were optimized, a classification accuracy of 100% for the tested samples. We especially discuss in the paper, the effect of spectrum normalization with an internal reference, the choice of input variables for the classification models and the optimization of parameters for the developed classification models. (C) 2017 Elsevier B.V. All rights reserved.
Duan, Y. X.
Laser-induced breakdown spectroscopy; Instrument; Review;IN-SITU ANALYSIS; INDUCED PLASMA; QUANTITATIVE-ANALYSIS; MICROCHIP-LASER; SPECTROCHEMICAL ANALYSIS; GEOLOGICAL SAMPLES; RAMAN-SPECTROSCOPY; MATRIX CONVERSION; RAPID DETECTION; LIBS SYSTEM
Laser-induced breakdown spectroscopy (LIBS) has become a very attractive technique in the field of chemical analysis. The technique utilizes a laser focused on a small spot to create a micro-plasma on the sample surface. In recent years, LIBS is a frontier analysis technique in spectrometric analysis, with the advantages such as real-time, online and non-contact analysis. The research and development of various instruments based on this technology has attracted great attention of analysts. In this article, we reviewed the research progress of LIBS instrument from aspects of the components and field equipment in recent years, including portable LIBS, handheld LIBS and remote LIBS.
GRADIENT-INDEX MICROLENSES; INTRAOCULAR LENSES; CONTACT-LENSES; POLY(METHYL METHACRYLATE); INDUCEDBREAKDOWN; FUSED-SILICA; WAVE-GUIDES; IN-VIVO; POLYMERS; INTERFEROMETRY
We describe the treatment of new hydrogels with nine different chemical compositions by femtosecond laser writing. The phase change induced in the wavefront when passing through the written areas was measured in all of these materials. The induced phase change is negative, which is attributed to the higher presence of water in the written regions and confirmed via Raman spectroscopy. The largest induced change in a single layer at 100 mm/s was -3.69 waves at 543 nm. These results show a strong dependence of the phase change on the concentration of some components and their molar ratio. We propose that some components are essential for the nonlinear energy absorption (""dopants""), while other components (""quenchers"") are essential in redirecting the absorbed energy to cause chemical reactions that profoundly change the polymer structure. (C) 2017 Optical Society of America
Deguchi, Y. ; Chong, D. T. ; Ikutomo, A. ; Liu, J. P. ; Liu, R. W. ; Shiou, F. J. ; Yan, J. J. ; Zhang, Z. Z.
Long pulse; dual-pulse laser-induced breakdown spectroscopy; DP-LIBS; enhancement; plasma temperature stabilization; underwater measurement;CO2-LASER PULSE; AMBIENT GAS; ABLATION; ENHANCEMENT; PRESSURES; FEASIBILITY; MAGNESIUM; DISCHARGE; SPECTRUM; LIQUIDS
Collinear long and short dual-pulse laser-induced breakdown spectroscopy (DP-LIBS) was employed to clarify the emission characteristics from laser-inducedplasma. The plasma was sustained and became stable by the long pulse-width laser with the pulse width of 60s under free running (FR) conditions as an external energy source. Comparing the measurement results of stainless steel in air using single-pulse LIBS (SP-LIBS) and DP-LIBS, the emission intensity was markedly enhanced using DP-LIBS. The temperature of plasma induced by DP-LIBS was maintained at a higher temperature under different gate delay time and short pulse-width laser power conditions compared with those measured using short SP-LIBS. Moreover, the variation rates of plasma temperatures measured using DP-LIBS were also lower. The superior detection ability was verified by the measurement of aluminum sample in water. The spectra were clearly detected using DP-LIBS, whereas it cannot be identified using SP-LIBS of short and long pulse widths. The effects of gate delay time and short pulse-width laser power were also discussed. These results demonstrate the feasibility and enhanced detection ability of the proposed collinear long and short DP-LIBS method.
Laser-induced breakdown spectroscopy; LIBS; multivariate analysis; soft independent modeling of class analogy; SIMCA; partial least squares discriminant analysis; PLS-DA; edible salt;INDUCED BREAKDOWN SPECTROSCOPY; SEA SALTS; LIBS; IDENTIFICATION; COMPACT; ORIGIN
We report soft independent modeling of class analogy (SIMCA) analysis of laser-induced plasma emission spectra of edible salts from 12 different geographical origins for their classification model. The spectra were recorded by using a simple laser-induced breakdown spectroscopy (LIBS) device. Each class was modeled by principal component analysis (PCA) of the LIBS spectra. For the classification of a separate test data set, the SIMCA model showed 97% accuracy in classification. An additional insight could be obtained by comparing the SIMCA classification result with that of partial least squares discriminant analysis (PLS-DA). Different from SIMCA, the PLS-DA classification accuracy seems to be sensitive to addition of new sample classes to the whole data set. This indicates that the individual modeling approach (SIMCA) can be an alternative to global modeling (PLS-DA), particularly for the classification problems with a relatively large number of sample classes.
LA-ICP-MS; INDIVIDUAL PARTICLES; ANALYTICAL-CHEMISTRY; FEMTOSECOND; GLASS; NANOSECOND; IONIZATION
Laser ablation - inductively coupled plasma -mass spectrometry (LA-ICP-MS) in tandem with laser induced breakdown spectroscopy (LIBS) was employed to chemically map and characterize uranium particles. The uranium particles were doped in various concentrations (0.01, 0.1, 1.0, and 2.0%) to a 50 : 50 Ni : Fe mixture. There was an excellent correlation in regards to concentration and the LA-ICP-MS measurements. In addition, the isotopic composition of the uranium particles was determined within 10% measurement uncertainty. LIBS measurements also showed strong agreement in the particle mapping when compared to the LA-ICP-MS analysis. Moreover, the total analysis time for a 5 x 5 mm area was only 50 minutes. These data suggest that the tandem LA-ICP-MS/LIBS technique can provide rapid and valuable information for nuclear material safeguards and actinide material characterization.
INDUCED BREAKDOWN SPECTROSCOPY; LASER-INDUCED FLUORESCENCE; EXCITED ATOMIC FLUORESCENCE; ELEMENTAL ANALYSIS; ABLATION; LIBS; SPECTROMETRY; MECHANISM; METALS; WASTE
Coupling laser-induced fluorescence to laser ablation can reduce detection limits relative to LIBS. The wing of the broadband similar to 193.3 nm emission from unmodified argon fluoride lasers can excite arsenic fluorescence via its 193.76 nm ground state transition for a simple fluorescence scheme. We present argon fluoride-excited laser-ablation laser-excited atomic fluorescence (LA-LEAF) measurements in steel and copper under argon and helium atmospheres. Because the ArF laser saturates the absorption transition and the steel samples show substantial nonspecific iron fluorescence, it is necessary to optimize the laser energy in addition to interpulse delay. LODs are slightly lower under helium (1.0 ppm in steel, 0.15 ppm in copper). These detection limits represent a modest improvement over previous LODs with LIBS, but suggest potential for improvement with line narrowing of the ArF laser.
IWDTF; LIBS; Animal manure composts; Cu; Zn;HEAVY-METAL CONTENTS; MULTIELEMENT ANALYSIS; ACCURACY IMPROVEMENT; MINERAL FERTILIZERS; LIVESTOCK FEEDS; TRACE-ELEMENTS; SPECTROMETRY; LIBS; CONTAMINANTS; TRANSFORM
Spectral denoising offers a basis for effective and accurate quantitative modeling of laser-induced breakdown spectroscopy (LIBS). To provide a solution for the defects of the traditional hard threshold function (HTF) and the soft threshold function (STF) for wavelet denoising methods, an improved wavelet dual threshold function (IWDTF) has been developed. Simulation analyses proved that the IWDTF could provide abetter denoising performance than the traditional functions. The IWDTF was applied to LIBS denoising and quantitative modeling of the Cu and Zn contents in representative Chinese aerobic composting samples. The results showed that the best spectral denoising effects for the Cu and Zn models were achieved when the adjustment parameters k(0), a, and theta were 0.9, 0.7 x lambda(1), and 0.1 x pi, and 0.2, 0.2 x lambda(1), and 0.1 x pi, respectively, and corresponding models' performances for Cu and Zn were both greatly improved, yielding R-p(2) of 0.9807 and 0.9177, RMSEP of 67.49 mg/kg and 84.92 mg/kg, and RPD of 3.12 and 3.07, respectively. (C) 2017 Published by Elsevier B.V.
Barros, A. I. ; Crespi, M. S. ; Ferreira, E. C. ; Junior, D. ; Neto, J. A. G. ; Ribairo, C. A. ; Senesi, G. S.
Biochar-based fertilizers; Calcium; Libs; Internal standardization;SPECTROMETRY; SOILS; COAL
Biochar has gained agricultural importance as a soil amendment because of its important agricultural properties such as water retention, plant nutrient supplier, promoter of microorganism growth, sequestration action of atmospheric CO2, etc. Further, it is a low cost material being produced by recycling. Due to its active sites, biochar can adsorb nutrients so acting as a soil fertilizer. Thus the rapid assessment of nutrients in these materials is essential to ensure quality control for agricultural purposes. This work aimed to develop a simple analytical method based on Laser-Induced Breakdown Spectroscopy (LIBS) to determine Ca in biochar-based fertilizers. In particular, biochar samples enriched with Ca were prepared from peanut shells, residues of eucalyptus and banana fibers. The calibration standards were prepared by matrix matching using a biochar from eucalyptus residues. Different spectral preprocessing were evaluated to enhance the precision and accuracy of the method. However, the matrix effects demanded the use of internal standardization as the appropriate methodology to obtain the best accuracy. A linear correlation coefficient of 0.989 and a linear work range of 1.51-11.23% Ca were obtained using the proposed method, which yielded limits of detection and quantification of 0.45% e 1.51%, respectively. Calcium contents determined by LIBS in biochar-based fertilizers were in good agreement (paired t-test at 95% confidence level) with those determined by using High-Resolution Continuous Source Atomic Absorption Spectrometry (HR-CS FAAS) as the reference technique. Thus, the importance of internal standardization was demonstrated to be successful for the quantitative analysis of Ca in complex matrices like biochar-based fertilizers. (C) 2017 Elsevier B.V. All rights reserved.
Hedwig, R. ; Jobiliong, E. ; Kagawa, K. ; Karnadi, I. ; Kurniawan, K. H. ; Lie, T. J. ; Lie, Z. S. ; Pardede, M. ; Suliyanti, M. M. ; Suyanto, H. ; Tjia, M. O. ; Wihardjo, E.
DUAL-PULSE LIBS; INDUCED PLASMA; ABLATION EFFICIENCY; SENSITIVE ANALYSIS; HELIUM PLASMA; FEMTOSECOND; ENHANCEMENT; NANOSECOND; MICROANALYSIS; DEUTERIUM
A time-resolved spectroscopic study is performed by using 125-500 micro-Joule (mu J) ps laser focused directly without the aid of microscope on a Cu plate sample in a variety of low-pressure ambient gases including air, helium and argon. It is shown that the ultrashort mu J laser-induced low-pressure plasma in Ar ambient gas exhibits the typical characteristics of shock wave plasma responsible for the thermal excitation and sharp emission of the analyte atoms. It is found that the highest signal to background (S/B) ratio of about 100 is achieved in 1.3 kPa argon ambient gas and detected with optical multichannel analyzer (OMA) gate delay of 1 ns and gate width of 50 mu s. The emission spectra obtained from pure Zn sample show the effective suppression of the ionic emission with ablation energy around and below 500 mu J. The experimental setup is successfully applied to Cr analysis with low detection limit in steel. In particular, its application to C analysis in steel is demonstrated to resolve the long standing problem of overlapping contributions from the neutral and ionic Fe emission. It is further found that an element of high excitation energy such as fluorine (F) can be clearly detected from a non metal teflon sample. Further, its application to alluminum sample containing various concentrations of Mg, Ca, Fe, and Si impurity elements clearly displays the existence of linear calibration lines promising for quantitative analyses in certain dynamical ranges. Finally, in view of the tiny crater sizes of less than 10 mu m diameter created by the very low ps laserenergy, this technique is promising for micrometer resolution mapping of elemental distribution on the sample surface and its depth profiling. (C) 2017 The Japan Society of Applied Physics
URANIUM; LIBS; FLUORESCENCE; SPECTROMETRY; MATRICES; SAMPLES; SYSTEM; PULSE; UF6
A hand-held device for laser-induced breakdown spectroscopy has been investigated for the determination of uranyl fluoride surface contamination. This research demonstrates the ability to successfully detect uranium on surfaces when using a low resolving power (lambda/Delta lambda = 4000) spectrograph, with a 5 mJ energy per 1 ns pulsed laser radiation, available as a commercially packaged hand-held system. Sand/uranyl fluoride mixtures are prepared to simulate residue likely encountered during decontamination efforts at facilities that handle uranium hexafluoride. Detection limits are described for four uranium lines with one revealing the capability to detect uranium at a level of 250 parts per million. Advantages of the studied compact device include that location specific information can be obtained on-site to augment contamination identification. (c) 2017 Optical Society of America
INDUCED BREAKDOWN SPECTROSCOPY; YAG LASER; EMISSION SPECTROSCOPY; PLANT MATERIALS; HYDROGEN; DEUTERIUM; RESIDUES; ABLATION; NITROGEN
We report the experimental evidence of shock wave plasma generation by direct observation of the plasma propagation using 68 mJ 1064 nm Nd-doped yttrium aluminum garnet laser irradiation on a relatively soft organic sample in He ambient gas at 2 kPa. The density jump associated with the arrival of the plasma front at a certain position is detected by means of the highly sensitive interferometric technique, in conjunction with the observation of the first appearance of the plasma emission at the same position and time of the plasma front arrival. The result shows that the plasma front moves at the Sedov speed, which is typical of shock wave propagation, yielding an excellent emission spectrum for the harder sample. The shock front speed is further found to decrease in the case of a softer sample, resulting in lesser spectroscopic performance, as demonstrated by the emission spectra measured from mochi samples of different hardnesses. The result of this study is promising for paving the way to extending the laser-induced breakdown spectroscopy application to the much needed spectrochemical analysis of agricultural and food products. (c) 2017 Optical Society of America
Dong, L. ; Hou, J. J. ; Hou, Z. Y. ; Jia, S. T. ; Ma, W. G. ; Wang, Z. ; Yang, G. Y. ; Yin, W. B. ; Zhang, L.
QUANTITATIVE-ANALYSIS; PARAMETERS; SAMPLES; LIBS
A calibration method based on homogeneous material for correcting laser-induced breakdown spectroscopy (LIBS) measurement-error bias in the case of dust pollution under laboratory conditions is proposed. The measured plasma spectra of the sample can be corrected by measuring the spectral integral of the homogeneous material. Thus, we can effectively minimize the dust pollution effect on LIBS and guarantee its precision. Results show that the mean absolute errors of CaO, MgO, Fe2O3, Al2O3, and SiO2 in cement samples are decreased notably from 1.02%, 0.06%, 0.15%, 0.57%, and 0.80% to 0.41%, 0.02%, 0.04%, 0.35%, and 0.39%, respectively. Combination of this calibration method with the traditional optical dustproof methods will significantly extend the LIBS equipment maintenance cycle and make preliminary preparations for the next practical industrial application. (C) 2017 Optical Society of America
Grishin, M. Y. ; Cheverikin, V. V. ; Peshin, M. ; Sdvizhenskii, P. A. ; Stavertiy, A. Y. ; Taksanc, M. V. ; Tretyakov, R. S.
HIGH-SPATIAL-RESOLUTION; STEEL-INDUSTRY; CHEMICAL MAPS; SPECTROMETRY; PLASMA; IDENTIFICATION; LIBS; MICROANALYSIS; CONVERTERS; SAMPLES
Three-dimensional multi-elemental mapping of composite wear-resistant coatings by laser-induced breakdown spectroscopy has been demonstrated for the first time, to the best of our knowledge. Individual clads of 1560 nickel alloy reinforced with tungsten carbide were synthesized by a co-axial laser cladding technique. Electron energy dispersive x-ray spectroscopy revealed elemental maps for major elements (W, Ni, Co, Cr, Fe) but failed to measure silicon and carbon. Laser-induced breakdown spectroscopy was utilized for elemental mapping of carbon and all other elements of interest. It was demonstrated that three-dimensional elemental profiling for a few tens of micrometers requires substantial laser spot overlapping during the scanning procedure in order to achieve good accuracy of depth measurements. Elemental maps for nickel, iron, chromium, silicon, tungsten, and carbon were quantified for 900 mu m x 900 mu m x 45 mu m volume with 30 mu m lateral and 4 mu m depth resolution in the case of tungsten carbide particles in nickel alloy. (C) 2017 Optical Society of America
Lead-free ferroelectrics; Cation vacancies; Laser-induced breakdown spectroscopy; Dielectric measurements;INDUCED BREAKDOWN SPECTROSCOPY; FREE PIEZOELECTRIC CERAMICS; SODIUM-POTASSIUM NIOBATE; ELECTRICAL-PROPERTIES; (K0.5NA0.5)NBO3 CERAMICS; NA0.5K0.5NBO3 CERAMICS; PHASE-TRANSITIONS; MICROSTRUCTURE; TEMPERATURE; PZT
The formation of cation vacancies can be useful for electro-chemical devices. In this regard, an understanding of vacancy formation is an important subject for enhancing current electrochemical devices and for developing next generation energy devices. In this work, we chose the well-known lead-free ferroelectric (K0.5Na0.5)NbO3 (KNN) as a model system to understand both the formation of cation vacancies and the relationship between cation vacancies and the physical properties. We studied sintering-duration dependence of the dielectric properties and the cation contents of KNN ceramics at the temperatures near the melting point of KNN. The difference in sintering duration led to a drastic change in the dielectric property, as well as to the creation of cation vacancies. Interestingly, we observed unequal evaporation of cations during the sintering process, which was confirmed by the data obtained from laser-inducedbreakdown spectroscopy. In addition, we found more drastic changes in the imaginary dielectric constant, which were likely due to a decrease in ionic conducting species, such as K and Na, in KNN.
laser-induced breakdown spectroscopy; eutectic glass; bioactive materials;FLOATING-ZONE TECHNIQUE; WOLLASTONITE-TRICALCIUM PHOSPHATE; EUTECTIC GLASS-CERAMICS; ND3+ IONS; WAVE-GUIDES; IN-VIVO; BIOCERAMICS; COMPOSITE; STRESSES; GROWTH
Laser-induced breakdown spectroscopy (LIBS) is applied to characterize the formation of porous hydroxyapatite layers on the surface of 0.8CaSiO(3)-0.2Ca(3)(PO4)(2) biocompatible eutectic glass immersed in simulated body fluid (SBF). Compositional and structural characterization analyses were also conducted by field emission scanning electron microscopy (FESEM), energy dispersive X-ray spectroscopy (EDX), and micro-Raman spectroscopy.
Laser induced breakdown spectroscopy (LIBS); Quantitative analysis; Matrix effect; Self-absorption;INDUCED PLASMA SPECTROSCOPY; ARTIFICIAL NEURAL-NETWORK; LEAST-SQUARES REGRESSION; ELEMENTAL ANALYSIS; MULTIVARIATE-ANALYSIS; EMISSION-SPECTROSCOPY; SPECTRAL-LINE; SOIL SAMPLES; IRON-ORE; CHEMCAM INSTRUMENT