A comparison of laser ablation inductively coupled plasma mass spectrometry, micro X-ray fluorescence spectroscopy, and laser induced breakdown spectroscopy for the discrimination of automotive glass

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), micro X-ray fluorescence spectroscopy (mu XRF), and laser induced breakdown spectroscopy (LIBS) are compared in terms of discrimination power for a glass sample set consisting of 41 fragments. Excellent discrimination results (>99% discrimination) were obtained for each of the methods. In addition, all three analytical methods produced very similiar discrimination results in terms of the number of pairs found to be indistingushable. The small nuber of indistingushable pairs that were identified all originated from the same vehicle. The results also show a strong correlation between the data generated from the use of mu XRF and LA-ICP-MS, when comparing mu XRF strontium intensities to LA-ICP-MS strontium concentrations. A 266 nm laser was utilized for all LIBS analyses, which provided excellent precision (<10% RSD for all elements and <10% RSD for all ratios, N=5). The paper also presents a thorough data analysis review for forensic glass examinations by UBS and suggests several element ratios that provide accurate discrimination results related to the LIBS system used for this study. Different combinations of 10 ratios were used for discrimination, all of which assisted with eliminating Type I errors (false exclusions) and reducing Type II errors (false inclusions). The results demonstrate that the LIBS experimental setup described, when combined with a comprehensive data analysis protocol, provides comparable discrimination when compared to LA-ICP-MS and mu XRF for the application of forensic glass examinations. Given the many advantages that LIBS offers, most notably reduced complexity and reduced cost of the instrumentation, LIBS is a viable alternative to LA-ICP-MS and mu XRF for use in the forensic laboratory. (C) 2008 Elsevier B.V. All rights reserved.