title: Adsorption saturation and chromatographic distortion effects on passive headspace sampling with activated charcoal in fire debris analysis.
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 microL (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.
authors.affiliation: Department of Chemistry, National Center for Forensic Science, University of Central Florida, P.O. Box 162367, Orlando, FL 32816-2367, USA.
authors.forename: Mary R
authors.initials: MR
authors.lastname: Williams
authors.forename: Denise
authors.initials: D
authors.lastname: Fernandes
authors.forename: Candice
authors.initials: C
authors.lastname: Bridge
authors.forename: Derek
authors.initials: D
authors.lastname: Dorrien
authors.forename: Stefanie
authors.initials: S
authors.lastname: Elliott
authors.forename: Michael
authors.initials: M
authors.lastname: Sigman