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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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. 

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.

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%.

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.

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.

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.