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Forensic science analysis of soil samples for the presence of flammable liquids occasionally results in the detection of volatile mixtures that lack some of the diagnostic features of common petroleum products. The presence of these mixtures is not consistent with evaporation or with a chemical or physical process, but is reported in microbiological literature that addresses bacterial degradation. Microbiological research has shown that crude oil spilled in the environment is sometimes degraded by bacteria. A study was conducted to demonstrate how automotive gasoline is degraded. Gasoline was spiked into 36 containers of soil (12 were stored at −5°C; 12 were stored at room temperature; and 12 of the soil samples were sterilized prior to the addition of the gasoline and were then stored at room temperature). These samples were monitored, and the results were compared using static heated headspace sampling and capillary gas chromatography. The gasoline in the unsterilized samples stored at room temperature degraded rapidly, while the gasoline in the other two sets of samples was unaffected. This degradation followed trends that can be recognized in casework and can assist in the identification of affected petroleum product residues in soil.

Capillary gas chromatography was usd to compare the relative concentrations of hydrocarbons in a variety of gasoline samples. It was found that most of the discriminating information is contained in the fraction with a volatility ranging from approximately n-pentane to n-octane. Using the described comparison method, all gasoline samples collected at random were easily distinguished. Gasolines with identical histories (from the same distributor and same lot), once added to a gasoline station residual, were also distinguishable, although not as readily as those samples obtained at random.

When comparing gasoline recovered from a fire scene with a possible source, several factors must be considered, including the variability introduced by the recovery method, possible contamination of the data by pyrolysis products, distortion of the data as a result of evaporation of the gasoline, and other alterations of the recovered gasoline by chemical and physical interactions. All of these factors can contribute to a decrease in the specificity of comparisons of gasoline recovered from fire debris relative to liquid gasoline comparisons.