Speedy Vapor Collection Technique Could Aid Arson Investigations

Arson investigators often decide whether foul play occurred in a fire by studying charred debris containing traces of an ignitable liquid such as gasoline or kerosene. Gas chromatography is the most common technique used to examine fire debris, and it requires sampling the volatile compounds in the air, or headspace, directly above a confined sample. But sampling may take hours and not be sensitive enough. With the goal of speedier, more sensitive analysis, Thomas J. Bruno and colleagues at the National Institute of Standards & Technology evaluated a vapor collection method involving porous layer open tubular chromatography columns containing different sorbents and maintained at cryogenic temperatures, which they call PLOT-cryo (J. Chromatogr. A 2014, DOI: 10.1016/j.chroma.2014.01.080). PLOT-cryo is an extension of established sampling methods and was previously evaluated as a way to find explosives, among other applications. The NIST team set fire to wood and carpet samples with 11 flammable fluids then analyzed samples with PLOT-cryo or traditional vapor collection techniques. PLOT-cryo outperformed the conventional methods, with sampling times as short as three minutes. The team has filed for a patent on an inexpensive portable PLOT-cryo device.