Interference from combustion residues of polystyrene-butadiene involving ‘alkylbenzenes’ in molecules on gasoline identification

Abstract

ABSTRACT The interference of background at fire scene on identification of ignitable liquid residues (ILRs) is an ongoing concern in fire investigation. The current study aims to determine potential interference on gasoline identification from the combustion/pyrolysis products of polystyrene-butadiene rubber (SBr) involving ‘alkylbenzenes’ in molecules. Gas chromatography–mass spectrometry (GC/MS) analysis results of extracts from combustion residues of SBrs, SBrs loaded with gasoline and gasoline were compared. Commonly encountered compounds interfering gasoline identification, including the alkylbenzenes, naphthalenes, as well as indanes, were obtained in all the combustion residues of the SBrs by analysing the extracted ion chromatogram (EICs) of the combustion/pyrolysis products. Furthermore, for gasoline loaded onto SBr substrate, the SBr causes significant distortion to gasoline combustion residues by changing the comparative contents of the target compounds for gasoline identification. Overreliance on the target compounds for gasoline identification could lead to misidentifications in the presence of SBrs combustion residues, while the typical ratios of the target compounds in gasoline combustion residues would also be affected when encountered with SBrs, especially for the cases of smaller loading of gasoline. A detailed examination of the C3-alkylbenzenes and C4-alkylbenzenes profile should be part of any fire debris analysis.