Adsorption saturation and chromatographic distortion effects on passive headspace sampling with activated charcoal in fire debris analysis

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Adsorption saturation and chromatographic distortion effects on passive headspace sampling with activated charcoal in fire debris analysis Williams MR, Fernandes D, Bridge C, Dorrien D, Elliott S, Sigman M
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Abstract
Distortion of the chromatographic profile obtained for hydrocarbons that have been sampled by adsorption onto activated charcoal is a well-known phenomenon. The work reported here helps to better define the causes of chromatographic profile distortion and offers a potential method to avoid chromatographic distortion in some cases through a subsampling technique. The recovery of hydrocarbons from an equimolar mixture was investigated to determine the influence of hydrocarbon concentration on the molar ratios of recovered components. In a one-quart container, hydrocarbon volumes as small as 24 mL (liquid) were sufficient to saturate the surface area available for adsorption on a 99.0 mm² square of activated charcoal, resulting in significant distortions in the molar ratio and the chromatographic profile of the recovered hydrocarbons. Passive headspace sampling of a similarly small volume of unweathered gasoline spiked onto carpet padding resulted in a significant distortion of the chromatographic profile. The chromatographic profile of the recovered hydrocarbons closely resembled 75% weathered gasoline. Heating the container spiked with unweathered gasoline to evenly distribute the components and then removing a subsample of the carpet padding to a second container for passive headspace analysis greatly reduced the amount of distortion in the resulting chromatogram.

Keywords:
activated charcoal, fire debris, forensic science, passive headspace
ISSN: 0022-1198
Paper ID: JFS2004274
DOI: 10.1520/JFS2004274

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Author Williams MR, Fernandes D, Bridge C, Dorrien D, Elliott S, Sigman M Title Adsorption saturation and chromatographic distortion effects on passive headspace sampling with activated charcoal in fire debris analysis Symposium , Committee on

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