NCJ Number
164332
Journal
Journal of Forensic Sciences Volume: 41 Issue: 3 Dated: (May 1996) Pages: 361-370
Date Published
1996
Length
10 pages
Annotation
This study will be presented in two articles; this first part addresses the effects of time, temperature, strip size, and sample concentration on the adsorption of common accelerants, with the intent of optimizing the analysis procedure; the second article will examine the dynamics of passive diffusion adsorption in detail, so as to explain the process and its effects.
Abstract
An adsorption process that would provide a reasonable sampling of volatiles components in the range of C5-C20 would be ideal. This study shows that in order to obtain a representative sample, all the parameters associated with the extraction must be considered. There are a number of time, temperature, strip size, and concentration combinations that could be used; however, other factors, including efficiency, cost-effectiveness, and practicality should also be considered. Samples that contain high levels of light petroleum products, gasoline, or medium-range petroleum products are prone to displacement and therefore require shorter adsorption times, lower temperatures, or larger charcoal strips to minimize the effect. Preliminary screening of samples prior to or during the adsorption process allows the analyst to determine the proper combination of adsorption parameters. The combination of time and temperature for the adsorption process should allow for the adsorption of heavier components without significantly contributing to the displacement of the lighter components. Higher temperatures (over 90 degrees C) are not recommended, because they promote the degradation and pyrolysis of substrates, further complicating the separation and identification processes. The size of the activated charcoal strip used in the analysis has a significant bearing on the efficiency of the extractions and cost of the analysis. Larger strip sizes are not only more expensive, but require more solvent for desorption, thus increasing the volume of potentially toxic and hazardous solvent being used; however, smaller strip sizes saturate quickly and thus begin displacement at lower concentrations. An 8 mm x 8 mm strip is recommended as the minimum amount of charcoal for analysis of debris in quart or gallon size containers. The composition of the substrate should also be considered. 8 figures and 17 references