Department of Chemistry and Biochemistry, Florida International University, Miami, FL 33199, USA.
Anal Bioanal Chem. 2011 Jul;400(10):3341-51. doi: 10.1007/s00216-011-4869-7. Epub 2011 Apr 2.
A method for the quantitative elemental analysis of surface soil samples using laser-induced breakdown spectroscopy (LIBS) was developed and applied to the analysis of bulk soil samples for discrimination between specimens. The use of a 266 nm laser for LIBS analysis is reported for the first time in forensic soil analysis. Optimization of the LIBS method is discussed, and the results compared favorably to a laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) method previously developed. Precision for both methods was <10% for most elements. LIBS limits of detection were <33 ppm and bias <40% for most elements. In a proof of principle study, the LIBS method successfully discriminated samples from two different sites in Dade County, FL. Analysis of variance, Tukey's post hoc test and Student's t test resulted in 100% discrimination with no type I or type II errors. Principal components analysis (PCA) resulted in clear groupings of the two sites. A correct classification rate of 99.4% was obtained with linear discriminant analysis using leave-one-out validation. Similar results were obtained when the same samples were analyzed by LA-ICP-MS, showing that LIBS can provide similar information to LA-ICP-MS. In a forensic sampling/spatial heterogeneity study, the variation between sites, between sub-plots, between samples and within samples was examined on three similar Dade sites. The closer the sampling locations, the closer the grouping on a PCA plot and the higher the misclassification rate. These results underscore the importance of careful sampling for geographic site characterization.
利用激光诱导击穿光谱（LIBS）对表层土壤样品进行定量元素分析的方法已经开发出来，并应用于批量土壤样品的分析，以区分样本。首次报道了在法医土壤分析中使用 266nm 激光进行 LIBS 分析。讨论了 LIBS 方法的优化，并将结果与之前开发的激光烧蚀电感耦合等离子体质谱（LA-ICP-MS）方法进行了比较。对于大多数元素，两种方法的精密度均<10%。LIBS 的检测限<33ppm，偏倚<40%，对于大多数元素。在一项原理验证研究中，LIBS 方法成功区分了来自佛罗里达州戴德县两个不同地点的样本。方差分析、Tukey 事后检验和学生 t 检验导致 100%的区分，没有第一类或第二类错误。主成分分析（PCA）导致两个地点的明显分组。线性判别分析的留一法验证得到了 99.4%的正确分类率。当使用 LA-ICP-MS 分析相同的样本时，也得到了类似的结果，表明 LIBS 可以提供与 LA-ICP-MS 类似的信息。在法医采样/空间异质性研究中，在三个类似的戴德地点上研究了地点之间、子区域之间、样本之间和样本内部的变化。采样位置越近，PCA 图上的分组越接近，误分类率越高。这些结果强调了仔细采样对于地理地点特征描述的重要性。
