Abstract
Classification of un-weathered ignitable liquids is a problem that is currently addressed by visual pattern recognition under the guidelines of Standard Test Method for Ignitable Liquid Residues in Extracts from Fire Debris Samples by Gas Chromatography-Mass Spectrometry, ASTM E1618-14. This standard method does not separately address the identification of substrate pyrolysis patterns. This report details the use of a Kohonen self-organizing map coupled with extracted ion spectra to organize ignitable liquids and substrate pyrolysis samples on a two-dimensional map with groupings that correspond to the ASTM-classifications and separate the substrate pyrolysis samples from the ignitable liquids. The component planes give important information regarding the ions from the extracted ion spectra that contribute to the different classes. Some additional insight is gained into grouping of substrate pyrolysis samples based on the nature of the unburned material as a wood or non-wood material. Further subclassification was not apparent from the self-organizing maps (SOM) results.
Highlights
Fire debris samples are currently classified according to ASTM E1618-14 which makes use of the total ion chromatogram, extracted ion chromatogram, and target compounds [1]
Ignitable liquid residues are classified as one of the following seven classes given by ASTM E1618-14: gasoline (GAS), petroleum distillates (PD), isoparaffinic products (ISO), aromatic products (AR), naphthenic-paraffinic products (NP), normal alkanes products (NORMA), and oxygenated solvents (OXY)
The neighborhood function defines the extent that the weight vectors of the surrounding neurons will be updated with respect to the distance from the winning neuron
Summary
Fire debris samples are currently classified according to ASTM E1618-14 which makes use of the total ion chromatogram, extracted ion chromatogram, and target compounds [1]. The chromatographic profiles and the relative presence of the major compound types are used to classify the ignitable liquid (IL) residue. This work makes use of the extracted ion spectrum (EIS), a subset of the TIS, which is generated using the ions in Table 2 of ASTM E1618-14. These ions are representative of the major compounds types present in each of Separations 2018, 5, 52; doi:10.3390/separations5040052 www.mdpi.com/journal/separations
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