SPME–GC–MS analysis of fire debris: assessing sample transfer viability for automated analysis and the influence of sooty materials

Abstract

Arson investigation poses unique challenges in forensic science due to the destructive nature of fires, which can compromise physical evidence. It is one of the most challenging areas of forensic chemistry, frequently applied to identify flammable liquids in fire debris. SPME–GC–MS is one of the most applied techniques for this purpose. Automated SPME–GC–MS systems offer various advantages over manual versions, such as increased efficiency, reproducibility, precision, and reduced analysis time. However, samples are often not sent to the laboratory in vials appropriate for automated SPME, raising questions about the feasibility of transferring them to these headspace vials in the laboratory to take advantage of this automation. Another significant issue with this analytical technique is how highly adsorbent materials in the sample, such as sooty materials, can hinder SPME analyses by affecting analyte desorption and subsequent detection. This study addresses these crucial questions by evaluating sample losses and assessing the impact of sooty materials on results. It demonstrates that transferring fire debris samples is feasible, with minimal impact on chromatographic profiles even for unburned gasoline when exposed to the atmosphere for short periods. Burned gasoline can still be identified, despite some losses, even after more than 24 h. The study also demonstrated that the presence of sooty material can hinder analyte detection in direct SPME analysis, but this can be mitigated using nonpolar solvent extractions followed by analyses of the dried extract using the same analytical technique.