laser-induced breakdown spectrometry; chlorine; plants; concrete;SPECTROSCOPY

We consider collinear and orthogonal beam-convergence configurations in double-pulse laser-induced breakdown spectrometry (LIBS, also known as laser-spark emission spectrometry) for chlorine determination in plants and concrete from the Cl I 837.59 nm line. We have observed that the signal-to-noise ratio is not much lower for the orthogonal configuration due to spatial instability in the second breakdown. At the same time, suppression of interfering molecular bands in this configuration lets us improve the sensitivity of LIBS for chlorine determination in plant material.

laser-induced breakdown spectroscopy; plasma temperature; electron density; limit of detection;ND-YAG LASER; EMISSION

The plasma is generated by focusing a long-pulse (80 mu s) Nd:YAG laser on chromium-doped soil samples. The calibration curves are drawn using the intensity ratio of the chromium spectral line at 425.435 nm with the iron spectral line (425.079 nm) as reference. The regression coefficient of the calibration curve is 0.993, and the limit of detection is 16 mg/kg, which is 19% less than that for the case of a Q-switched laser In the method of long-pulse laser-inducedbreakdown spectroscopy, the laser-induced plasma had a temperature of 15795.907 K and an electron density of 2.988 x 10(17) cm(-3), which exceeded the corresponding plasma parameters of the Q-switched laser-induced breakdown spectroscopy by 75% and 24% respectively.

laser induced breakdown spectroscopy; teeth; caries; enamel; calcium; phosphorus; zinc;DENTAL-CARIES; ZINC-DEFICIENCY; ENAMEL; MODELS; SR

The aim of this work is a multi-component analysis of the element composition of the enamel and carious parts of teeth and the quantification of enamel demineralization using laser-induced breakdown spectroscopy (LIBS). For each tooth the P/Ca ratios of the emission line intensities in the enamel part and those in the carious regions were compared. Since zinc is a trace element, the same procedure was performed for Zn/Ca ratios in the enamel and carious parts. These comparisons showed that the mineral loss from carious lesions occurs at different rates for the studied elements. Calcium has the highest casualty rate. On the other hand, the zinc level diminishes also in the carious region but at a lower rate. The lines were obtained from plume plasma emission generated on the enamel and carious regions.

laser-induced breakdown spectroscopy; soil; manganese;QUANTITATIVE-ANALYSIS; LIBS; SAMPLES; ALLOY

Laser-induced breakdown spectroscopy (LIBS) has been applied to measure spectral characteristics and to perform quantitative analysis of the concentration of manganese in soil, an issue of great concern for precision agriculture. For the analysis, soil samples were compressed into pellets and a pulsed Nd:YAG laser was employed to produce the plasma in air at atmospheric pressure. Using this approach, we analyzed the time evolution of spectral characteristics and their dependence on the laser pulse energy. A calibration curve was constructed using reference sandy soil samples collected from a farm. An internal standard curve was used to improve the accuracy of the LIBS metrology for soil analyses. The results of this analysis demonstrated the usefulness of this method for analyzing the concentration of manganese in soil.

laser-induced breakdown spectroscopy; Pu'er tea leaves; quantitative measurement; external standard method; internal standard method; multiple linear regression method;WATER SOLUTION; LIBS; CALIBRATION; CHROMIUM; CR

Laser-induced breakdown spectroscopy (LIBS) is applied at natural atmosphere to compare the quantitative analysis performances of the toxic heavy metal element lead (Pb) in Pu'er tea leaves, determined by three calibration methods: the external standard method, the internal standard method, and the multiple linear regression method. The Pb I line at 405.78 nm is chosen as the analytical spectral line to perform the calibration. The linear correlation coefficients (R (2) ) of the predicted concentrations versus the standard reference concentrations determined by the three methods are 0.97916, 0.98462, and 0.99647, respectively. The multiple linear regression method gives the best performance with respect to average relative errors (ARE = 2.69%), maximum relative errors (MRE = 4.94%), average relative standard deviations (ARSD = 9.69%) and maximum relative standard deviations (MRSD = 24.44%) of the predicted concentrations of Pb in eight samples, compared to the other two methods. It is shown that the multiple linear regression method is more accurate and stable in predicting concentrations of Pb in Pu'er tea leaf samples.

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.

LIBS quantitative analysis; reduction of matrix effect; internal standard calibration; normalization; correction of self-absorption;PART II; SAMPLES; PARAMETERS

A procedure for matrix effect reduction is proposed to enhance the precision of quantitative analysis of metal alloys using laser-induced breakdownspectroscopy (LIBS). This procedure is based on a number of successive steps in order to correct the signal fluctuations caused by plasma interaction and the matrix effect. The first step is the selection of optimum parameter settings of the detection system, such as laser power, delay time, and focal distance. The second step is the estimation of the absolute or relative values of impurities on the basis of the internal standard calibration. The third step is the analysis of the metal basis of the alloy used as an internal standard, which requires spectrum averaging, whole integral spectrum normalization, and self-absorption correction. Three sets of metal-based alloys (aluminum, steel, and copper) are used in this investigation as reference standards for calibration and validation. Successive improvements of the quality of calibration curves are observed during the proposed procedure.

laser-induced breakdown spectroscopy; soil; magnesium; nonlinear multivariate calibration;RARE-EARTH-ELEMENTS; SAMPLES; LIBS; QUANTIFICATION; DIAGNOSIS; METALS

Laser-induced breakdown spectroscopy (LIBS) coupled with the nonlinear multivariate regression method was applied to analyze magnesium (Mg) contents in soil. The plasma was generated using a 100 mJ Nd:YAG pulsed laser, and the spectra were acquired using a multi-channel spectrometer integrated with a CCD detector. The line at 383.8 nm was selected as the analysis line for Mg. The calibration model between the intensity of characteristic line and the concentration of Mg was constructed. The traditional calibration curve showed that the concentration of Mg was not only related to the line intensity of itself, but also to other elements in soil. The intensity of characteristic lines for Mg (Mg I 383.8 nm), manganese (Mn) (Mn I 403.1 nm), and iron (Fe) (Fe I 407.2 nm) were used as input data for nonlinear multivariate calculation. According to the results of nonlinear regression, the ternary nonlinear regression was the most appropriate of the studied models. A good agreement was observed between the actual concentration provided by inductively coupled plasma mass spectrometry (ICP-MS) and the predicted value obtained using the nonlinear multivariate regression model. The correlation coefficient between predicted concentration and the measured value was 0.987, while the root mean square error of calibration (RMSEC) and root mean square error of prediction (RMSEP) were reduced to 0.017% and 0.014%, respectively. The ratio of the standard deviation of the validation to the RMSEP increased to 8.79, and the relative error was below 1.21% for nine validation samples. This indicated that the multivariate model can obtain better predicted accuracy than the calibration curve. These results also suggest that the LIBS technique is a powerful tool for analyzing the micro-nutrient elements in soil by selecting calibration and validation samples with similar matrix composition.

laser-induced breakdown spectroscopy; TEA CO2 laser-induced gas plasma; transversely excited atmospheric CO2 laser; powder analysis;INDUCED BREAKDOWN SPECTROSCOPY; SAMPLES; IDENTIFICATION; ABLATION; SOILS

Analysis of powder samples available in small quantities has been carried out using metal-assisted gas plasma by utilizing a transversely excited atmospheric (TEA) CO2 laser. The powder was homogeneously mixed with Si grease, and the mixed powder was painted on a metal subtarget. When a TEA CO2 laserwas directly focused on the metal subtarget at atmospheric pressure of He gas, a high-temperature He gas plasma was induced. It is assumed that the powder particles were vaporized to be effectively atomized and excited in the gas plasma region. This method has been employed in the rapid analyses of elements in organic and inorganic powder samples present in small quantities. Detection of trace elements of Cr and Pb has been successfully made by using the supplement powder and loam soil, respectively. The detection limits of Pb in loam soil were approximately 20 mg/kg.

laser-induced breakdown spectroscopy; principal component analysis; sedimentary rock; metamorphic rock; igneous rock;LIBS

This study deals with the analysis of rocks using laser-induced breakdown spectroscopy (LIBS) coupled with principal component analysis. The spectra of sedimentary, metamorphic, and igneous rock samples were recorded in the 200-900 nm spectral range. The atomic lines of elements such as Si, Ca, Mg, Fe, Na, and K along with lighter elements, namely C, H, N, and O, were observed in these spectra. Multivariate analysis in combination with LIBS was used to classify the samples. For principal component analysis, a 12 x 5849 data matrix was formed using the results of LIBS. The plot of the analysis revealed similarities between the sedimentary and metamorphic rock samples compared with the igneous rock sample. Thus, the present study demonstrates that LIBS coupled with principal component analysis can become an important tool for rapid classification and in-situ discrimination of rock samples.

laser-induced breakdown spectroscopy; plasma modeling; calibration-free approach; quality control of drugs; multivitamin tablet;RELATIVE OSCILLATOR-STRENGTHS; PRECISION-MEASUREMENT; TRACE-ELEMENTS; TRANSITIONS; ARGON

The feasibility of the compositional analysis of drugs by calibration-free laser-induced breakdown spectroscopy (LIBS) was investigated using multivitamin tablets as a sample material. The plasma was produced by a frequency-quadrupled Nd: YAG laser delivering UV pulses with a duration of 5 ns and an energy of 12 mJ, operated at a repetition rate of 10 Hz. The relative fractions of the elements composing the multivitamin drug were determined by comparing the emission spectrum of the laser-produced plume with the spectral radiance computed for a plasma in a local thermodynamic equilibrium. Fair agreement of the measured fractions with those given by the manufacturer was observed for all elements mentioned in the leaflet of the drug. Additional elements such as Ca, Na, Sr, Al, Li, K, and Si were detected and quantified. The present investigations demonstrate that laser-induced breakdown spectroscopy is a viable technique for the quality control of drugs.