Doctor of Philosophy (PhD)
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LA-ICP-MS, Elemental analysis, Milk powder, Elemental profiling, Forensic glass interpretation, Glass database
Date of Defense
The first study focuses on the development of a laser based method for the elemental analysis of solid milk powder. Milk powder samples originating from five different countries were analyzed to determine any geographic differences. A LA-ICP-MS method was developed and compared to k0-INAA for several milk samples as well as a reference sample. Precision of 10% RSD or better and a bias of 10% was achieved for both techniques for most elements with LA-ICP-MS producing lower limits of detection (~ 1 ppm) for Sr. The comparison of LA-ICP-MS to k0-INAA showed overlap of the 95% confidence intervals for all comparison samples. The data for 68 authentic milk powder samples representing 5 different countries (Argentina, Russia, Singapore, Slovenia, and the United States) was collected and used as a preliminary database. Principle component analysis (PCA) shows different groupings for the United States, Argentina, Singapore, and Slovenia. However the large number and geographic distribution of samples from Russia were not able to be distinguished from the samples from the United States and Slovenia.
The second study focuses on the use of trace element databases for the objective interpretation of forensic glass evidence. Ten laboratories conducting analysis of glass participated in three inter-laboratory exercises. The aims of these exercises were to evaluate the use of a standard method for the analysis and comparison of glass evidence and to investigate different statistical approaches for interpreting results. Elemental analysis was performed on 420 vehicle windshield samples collected from 210 different vehicles representing manufacturing dates between 2004-2017 and 26 vehicle manufacturers. Using a variation of a previously reported comparison criterion for comparing samples to a database, the false exclusion rate and false inclusion rate for the new vehicle database were calculated to be 1.9% and 0.1 % respectively. This criterion was used to calculate the frequency of an elemental profile for the case scenarios distributed as part of the inter-laboratory exercises. Similarities were observed between labs that calibrated their data the same way, thus showing it is possible for labs to use a central database.
Hoffman, Tricia Marie, "The Use of Elemental Databases in Forensic Science: Studies on Vehicle Glass Interpretation and Milk Powder Provenancing" (2018). FIU Electronic Theses and Dissertations. 3812.
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