Senior Criminalist, Orange County Sheriff/Coroner Department, Santa Ana, CA
(Received 14 December 1992; accepted 1 June 1993)
Ethyl chloride, in a blood sample, was identified as ethanol on three out of six occasions using headspace gas chromatography. The peak matching tolerance (PMT) for ethanol was set at approximately 0.500 min ±0.0225 min. Three test results fell within the PMT for ethanol. The retention time (RT) for these test results was 0.44 min, and the relative retention time (RRT) was 0.478 min. Three test results, however, fell outside the PMT for ethanol. Two had RTs of 0.48 min and RRTs of 0.523 min, and one had a RT of 0.44 min and a RRT of 0.476 min. To prevent ethyl chloride from being identified as ethanol, the PMT was changed to approximately 0.500 min ±0.012 min.
Mixture samples containing deionized water, ethyl chloride and ethanol were tested with the new PMT. Ethyl chloride and ethanol coeluted, forming one peak that was identified as ethanol. The peak areas of the two compounds in mixture were additive and gave falsely elevated ethanol results. The RT of the samples was 0.45 min and the RRT was 0.492 min ±0.005 min. Carrier gas flow rate was decreased, lengthening the RTs and RRTs, but this failed to separate the two compounds.
Paper ID: JFS13595J