Department of Chemistry and Biochemistry, and International Forensic Research Institute (IFRI), Florida International University, Miami, FL 33199, USA.
Forensic Sci Int. 2012 Apr 10;217(1-3):222-8. doi: 10.1016/j.forsciint.2011.11.009. Epub 2011 Dec 1.
The elemental analysis of glass evidence has been established as a powerful discrimination tool for forensic analysts. Laser ablation inductively coupled plasma optical emission spectrometry (LA-ICP-OES) has been compared to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and energy dispersive micro X-ray fluorescence spectroscopy (μXRF/EDS) as competing instrumentation for the elemental analysis of glass. The development of a method for the forensic analysis of glass coupling laser ablation to ICP-OES is presented for the first time. LA-ICP-OES has demonstrated comparable analytical performance to LA-ICP-MS based on the use of the element menu, Al (Al I 396.15 nm), Ba (Ba II 455.40 nm), Ca (Ca II 315.88 nm), Fe (Fe II 238.20 nm), Li (Li I 670.78 nm), Mg (Mg I 285.21 nm), Sr (Sr II 407.77 nm), Ti (Ti II 368.51 nm), and Zr (Zr II 343.82 nm). The relevant figures of merit, such as precision, accuracy and sensitivity, are presented and compared to LA-ICP-MS. A set of 41 glass samples was used to assess the discrimination power of the LA-ICP-OES method in comparison to other elemental analysis techniques. This sample set consisted of several vehicle glass samples that originated from the same source (inside and outside windshield panes) and several glass samples that originated from different vehicles. Different match criteria were used and compared to determine the potential for Type I and Type II errors. It was determined that broader match criteria is more applicable to the forensic comparison of glass analysis because it can reduce the affect that micro-heterogeneity inherent in the glass fragments and a less than ideal sampling strategy can have on the interpretation of the results. Based on the test set reported here, a plus or minus four standard deviation (± 4s) match criterion yielded the lowest possibility of Type I and Type II errors. The developed LA-ICP-OES method has been shown to perform similarly to LA-ICP-MS in the discrimination among different sources of glass while offering the advantages of a lower cost of acquisition and operation of analytical instrumentation making ICP-OES a possible alternative elemental analysis method for the forensic laboratory.
玻璃证据的元素分析已被确立为法医分析人员的有力鉴别工具。激光烧蚀电感耦合等离子体发射光谱（LA-ICP-OES）已与激光烧蚀电感耦合等离子体质谱（LA-ICP-MS）和能量色散微 X 射线荧光光谱（μXRF/EDS）进行了比较，作为玻璃元素分析的竞争仪器。首次提出了将激光烧蚀与 ICP-OES 相结合用于法医分析玻璃的方法。基于使用元素菜单，LA-ICP-OES 已证明与 LA-ICP-MS 的分析性能相当，Al（Al I 396.15nm）、Ba（Ba II 455.40nm）、Ca（Ca II 315.88nm）、Fe（Fe II 238.20nm）、Li（Li I 670.78nm）、Mg（Mg I 285.21nm）、Sr（Sr II 407.77nm）、Ti（Ti II 368.51nm）和 Zr（Zr II 343.82nm）。本文介绍了相关的衡量标准，如精密度、准确性和灵敏度，并与 LA-ICP-MS 进行了比较。使用一组 41 个玻璃样本评估了与其他元素分析技术相比，LA-ICP-OES 方法的鉴别能力。该样本集由来自同一来源（挡风玻璃内外）的几个车辆玻璃样本和来自不同车辆的几个玻璃样本组成。使用不同的匹配标准进行比较，以确定 I 型和 II 型错误的可能性。结果表明，更广泛的匹配标准更适用于玻璃分析的法医比较，因为它可以减少玻璃碎片固有微观不均匀性和不理想的采样策略对结果解释的影响。基于这里报道的测试集，一个正负四个标准差（±4s）的匹配标准产生了 I 型和 II 型错误的可能性最低。研究结果表明，所开发的 LA-ICP-OES 方法在鉴别不同来源的玻璃方面与 LA-ICP-MS 性能相当，同时具有较低的仪器购置和运行成本优势，使 ICP-OES 成为法医实验室中元素分析的一种可行替代方法。
