Differentiated factor expression by chemical class in the concentration of ignitable liquid residue by dynamic vapor microextraction

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Abstract

Ignitable liquids (IL) are complex mixtures whose chromatographic profiles may vary considerably across chemical compound classes. Dynamic vapor microextraction (DVME) is an emerging technique with potential application for extracting and concentrating IL from fire debris. A previous study assessed the effects of 11 instrumental and debris factors on DVME performance by collecting chromatographic data from a designed experiment, but did not investigate whether factor effects had differential expression within individual chemical classes. In this study, that experimental data is reanalyzed to assess factor effects individually in each of five chemical classes relevant to IL identification (alkanes, cycloalkanes & alkenes, aromatic-alkylbenzes, indanes, and polynuclear aromatics), and effects are compared to the results previously reported from the original analysis. Two new instrument settings (capillary vapor trap coating and temperature) are found to have significant class-specific effects, providing additional avenues of improving DVME performance, while the effect of collection volume is found to be discordant in one class (alkane) compared to all others. Effects from uncontrollable debris factors on DVME performance are also found to be partially mitigated in certain classes through optimal device settings, though "optimal" may depend on the sample being analyzed. This analysis offers new insight into DVME optimization and robustness, and provides a discussion on how experimental conclusions drawn from aggregate chromotographic data, without consideration of class-specific effects, may be incomplete.

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Keywords

Forensic Science and Chemistry

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