This study examined ways to preserve ignitable liquid residues (ILRs) by sterilizing fire debris samples without interfering with their subsequent analysis.
When a fire is suspected to be intentionally set, fire debris samples can be collected and analyzed for ignitable liquid residues (ILRs). In some cases, samples will contain highly organic substrates such as soil or rotting wood. These substrates will contain a high bacterial load, which can result in systematic and irreversible damage to the ILR due to microbial degradation. There are many methods for sterilizing soil reported in the literature, such as freezing, irradiation, autoclaving, and various chemical fumigation techniques; however, these methods either do not kill all bacterial species, cannot be easily applied in the field, or would interfere with the analysis of the ILRs. In the current study, various anti-microbial compounds, including triclosan (2,4,4′-trichloro-2′-hydroxydiphenyl ether), were tested for their effectiveness in killing bacteria present in the soil. Triclosan was effective in qualitative growth studies and was therefore used to measure bacterial growth (or lack thereof) by spectroscopic analysis as well as passive headspace analysis. These experiments showed that triclosan was able to sterilize soil samples in less than 60 s, maintain their sterility for at least 77 hours, and preserve gasoline residues on a soil matrix for at least 30 days. (publisher abstract modified)