The Interference from Typical Tire Combustion Products on Gasoline Identification in Forensic Fire Investigations

Rubber is prone to introduce matrix interference on gasoline identifications due to its petrochemical origin. As a typical rubber product, automobile tire is also commonly extracted physical evidence in automobile fire scenes. On account of the various rubber components in tires of different parts and brands, the characteristic compounds extracted in their corresponding residues also differ since combustion products are closely related to chemical components, which may lead to different extents of interference. The research herein qualitatively analyzed the combustion residues of tires with and without gasoline via gas chromatography–mass spectrometry (GC–MS). Alkylbenzenes, condensed ring aromatics and the homolog of indanes generated during the combustion of tires notably interfered with gasoline identifications. Specifically, more types of C 4 -alkylbenzenes were detected in treads than sidewalls did. The residues of tires and gasoline can be distinguished by P-phenylenediamine and long-chain alkanes (C 11 ~ C 15 ). When loaded with gasoline, some diagnostic PAHs for gasoline identifications were absent, causing a negative effect on fire debris analysis. Compared with Michelin tires, the EIC of PAHs was more severely distorted due to the involvement of Kumho tires. The experimental data and conclusions about the interference from tires on gasoline identifications can provide solid supports for debris identifications practically.