Influence of chemical structure of SBr on the interference to gasoline identification for fire debris analysis

Abstract

To examine the relationship between the molecular composition of interferents and their interference on gasoline identification in fire debris analysis, we conducted free burning experiments using five polystyrene-butadienes (SBrs) with styrene contents ranging from 9.5 wt% to 40 wt%. The combustion residues of these SBrs with and without the presence of gasoline were analyzed via gas chromatography-mass spectrometry. The compounds frequently used for gasoline identification, were detected in all the SBr combustion residues, and the Pearson product moment correlation coefficients have been calculated to quantify the interference extent based on the relative peak area ratios of the characteristic compounds. When gasoline is loaded onto these SBrs, particular attention should be paid since the relative content of the compounds of interest changed significantly, which distorted the chromatogram profile of gasoline greatly. Combining the above analysis results, we can confirm that materials containing “alkylbenzene” in their molecular structure are likely to result in both false positive and false negative identifications when determining the presence of ignitable liquid. Additionally, the interference extent varies with the molecular composition of the interferents. This further emphasizes the importance of considering the molecular structure when assessing the interference caused by these materials.