INDUCED BREAKDOWN SPECTROSCOPY; MULTIELEMENT; SAMPLES; CARBON; LINES

The laser induced breakdown spectroscopy (LIBS) technique is an effective method to detect material composition by obtaining the plasma emission spectrum. The overlapping peaks in the spectrum are a fundamental problem in the qualitative and quantitative analysis of LIBS. Based on a curve fitting method, this paper studies an error compensation method to achieve the decomposition and correction of overlapping peaks. The vital step is that the fitting residual is fed back to the overlapping peaks and performs multiple curve fitting processes to obtain a lower residual result. For the quantitative experiments of Cu, the Cu-Fe overlapping peaks in the range of 321-327 nm obtained from the LIBS spectrum of five different concentrations of CuSO4 . 5H(2)O solution were decomposed and corrected using curve fitting and error compensation methods. Compared with the curve fitting method, the error compensation reduced the fitting residual about 18.12-32.64% and improved the correlation about 0.86-1.82%. Then, the calibration curve between the intensity and concentration of the Cu was established. It can be seen that the error compensation method exhibits a higher linear correlation between the intensity and concentration of Cu, which can be applied to the decomposition and correction of overlapping peaks in the LIBS spectrum. (c) 2017 Optical Society of America

LIBS; Continuous background; Interpolation method; Quantitative;MODEL-FREE ALGORITHM; QUANTITATIVE-ANALYSIS; TRACE-ELEMENTS; CU; REGRESSION; SAMPLES; METALS; LIBS

Laser-induced breakdown spectroscopy (LIBS) is an analytical technique that has gained increasing attention because of many applications. The production of continuous background in LIES is inevitable because of factors associated with laser energy, gate width, time delay, and experimental environment. The continuous background significantly influences the analysis of the spectrum. Researchers have proposed several background correction methods, such as polynomial fitting, Lorenz fitting and model-free methods. However, less of them apply these methods in the field of LIBS Technology, particularly in qualitative and quantitative analyses. This study proposes a method based on spline interpolation for detecting and estimating the continuous background spectrum according to its smooth property characteristic. Experiment on the background correction simulation indicated that, the spline interpolation method acquired the largest signal-to-background ratio (SBR) over polynomial fitting, Lorenz fitting and model-free method after background correction. These background correction methods all acquire larger SBR values than that acquired before background correction (The SBR value before background correction is 10.0992, whereas the SBR values after background correction by spline interpolation, polynomial fitting, Lorentz fitting, and model-free methods are 26.9576, 24.6828,18.9770, and 25.6273 respectively). After adding random noise with different kinds of signal-to-noise ratio to the spectrum, spline interpolation method acquires large SBR value, whereas polynomial fitting and model-free method obtain low SBR values. All of the background correction methods exhibit improved quantitative results of Cu than those acquired before background correction (The linear correlation coefficient value before background correction is 0.9776. Moreover, the linear correlation coefficient values after background correction using spline interpolation, polynomial fitting, Lorentz fitting, and model-free methods are 0.9998, 0.9915, 0.9895, and 0.9940 respectively). The proposed spline interpolation method exhibits better linear correlation and smaller error in the results of the quantitative analysis of Cu compared with polynomial fitting, Lorentz fitting and model-free methods, The simulation and quantitative experimental results show that the spline interpolation method can effectively detect and correct the continuous background. (C) 2017 Elsevier B.V. All rights reserved.

Laser-induced breakdown plasma spectrometry; laser ablation; surface oxide layer; Fe-Ni alloy; Fe-Cr alloy;INDUCED PLASMA SPECTROMETRY; SELF-ABSORPTION; SPECTROSCOPY; CALIBRATION; COPPER

This paper describes the fundamental process of laser ablation occurring in a laser-induced plasma. The sampling process in laser-induced breakdownplasma spectrometry is very complicated and thus has not been fully understood. Our study focused on a relationship between the composition of ablation amounts and the bulk composition, when Fe-based binary alloys were employed as test samples. For this purpose, the ablation amounts of constituent elements in the alloys were determined by ICP-OES, through a method in which ablated deposits by laser irradiation were collected on a glass plate and then dissolved in an acid solution. In Fe-Ni binary alloys, the Ni content in the ablated deposits was almost the same as the bulk composition, which implied that Ni and Fe atoms evaporated along with the chemical composition of the samples; however, in Fe-Cr binary alloys, the Cr content in the ablated deposits was half of the bulk composition, probably because Cr atoms were difficult to be released from the sample surface. X-ray photoelectron spectra of ablated Fe-Cr alloy samples indicated that the resultant surface layer after laser irradiation comprised a thin oxide layer, consisting of Cr2O3 and FeO, and a relatively thick oxide layer beneath the outermost surface oxide, of which the composition was a complex of Cr2O3, Fe and FeO. The reason for this is that the dissociation energy of Cr2O3 is obviously higher than that of FeO, and thus Cr2O3 decomposed with more difficulty and thus left preferentially in a surface oxide layer of the Fe-Cr alloys. As a result, the Cr2O3 layer could suppress the ablation of Cr.

PLASMA-MASS SPECTROMETRY; VACUUM-ULTRAVIOLET; ABLATION; STEEL; COAL

The laser-induced breakdown spectroscopy (LIBS) with a frequency quintupled 213 nmNd:YAG laser was examined to the analysis of trace level of carbon (C) in high-purity metals and its detection and analytical capabilities were evaluated. Though C signal in a wavelength of 247.9 nm, which showed the highest sensitivity of C, could be obtained from Cd, Ti, and Zn ca. 7000 mg kg(-1) C in Fe could not be detected due to the interferences from a lot of Fe spectra. Alternative C signal in a wavelength of 193.1 nm could not be also detected from Fe due to the insufficient laser output energy of the frequency quintupled 213 nm Nd:YAG laser. The depth analysis of C by LIBS was also demonstrated and the C in Cd and Zn was found to be contaminated in only surface area whereas the C in Ti was distributed in bulk. From these results, the frequency quintupled 213 nm Nd:YAG laser, which was adopted widely as a commercial laser ablation (LA) system coupled with inductively coupled plasma mass spectrometry (ICPMS) for trace element analysis in solid materials, could be used for C analysis to achieve simultaneous measurements for both C and trace elements in metals by LIBS and LA-ICPMS, respectively.