Laser induced breakdown spectroscopy as a tool for discrimination and quantitative characterization of glass for forensic applications.

摘要

Material analysis and characterization can provide important information as evidence in legal proceedings. Taking advantage of the multi-element detection capability and minimal to no sample preparation of LIBS, this technique is proposed as a viable alternative for glass analysis. Discrimination studies by linear and rank correlation methods were performed to glasses from automobile windows. Linear correlation combined with the use of a spectral mask, which eliminates some high-intensity emission lines from the major elements present in glass, provides effective identification and discrimination at a 95% confidence level. In the course of this study, several key instrumental parameters were identified and investigated, and a comparative study regarding the performance of up to four different commercial instruments for LIBS analysis of solids has been made. Results indicate that the spectral resolution and sensitivity of the systems were linked to the performance and suitability of the technique for material identification by correlation methods, especially when samples were of very similar composition.;While the qualitative characterization of materials without sample preparation is certainly one of the main advantages of LIBS, the possibility of performing accurate quantitative analysis relies on the use of calibration curves made with matrix-matched standards. Such quantitative analysis would also improve the discrimination capability of the technique in the case of the glass samples analyzed. Quantitation is one of the analytical aspects of LIBS where improvements are needed. In addition to the conventional analytical procedures followed in LIBS analysis, a normalization procedure based upon the possible correlation existing between the background fluctuation and the analytical signal. This method has been applied to several types of solid samples. The results of all these investigations have allowed a fair assessment of the applicability of LIBS for discrimination and quantitative characterization of solid samples in general, and glasses in particular.