Gas chromatography - mass spectrometry (GC-MS) is a common technique used in the analysis of fire debris. In this approach, the chromatogram of an ignitable liquid residue (ILR) extracted from the debris is visually compared to chromatograms of neat liquids in a reference collection. However, the association of the ILR to the neat liquid can be affected by factors such as matrix interferences, evaporation of the ignitable liquid, and thermal degradation. This research aims to develop an objective method for associating ILRs to the corresponding ignitable liquid standard using multivariate statistical procedures. The combination of statistical procedures removes subjectivity in visual comparison of chromatograms, while enabling a statistical measure of the association between the ILR and the corresponding liquid standard. In this study, liquid standards of neat gasoline and kerosene, as well as each liquid at two different evaporation levels, were prepared. The neat and evaporated liquids were spiked onto unburned and burned samples of two different household matrices (nylon carpet and high density polyethylene). In addition, separate samples of each matrix were spiked with the ignitable liquids and then burned using a propane torch to simulate fire debris. A combination of principal components analysis (PCA) and Pearson product moment correlation (PPMC) coefficients was used to investigate the association of ILRs to the corresponding liquid standards. PCA was used to assess the association of the ILRs to the corresponding liquid standard, while PPMC coefficients provided a statistical measure of that association despite matrix interferences, evaporation effects, and thermal degradation.
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