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

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.

KEYWORDS:

• Fire debris analysis
• gasoline identification
• combustion residues
• alkylbenzenes in molecule
• polystyrene-butadiene rubber
• the intragroup and intergroup ratios

Acknowledgments

One of the authors, Jing Jin, is grateful to Dr. Wing Man Lee and Dr. Wong Koon-hung from the Government Laboratory of the Government of the Hong Kong Special Administration Region for language polishing.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported by the funds of key special programs of China People’s Police University (No. 2019zdgg003 and ZDZX202003), Ministry of Public Security of the People’s Republic of China (No. 2020JSYJC24) and Natural Science Foundation of Hebei Province (E2021507001).