Misidentification of ethyl chloride in the routine GC-FID analysis for alcohol

GC-FID is the method of choice for alcohol screening and quantitative analysis in modern forensic medical practice. Although specific enough for routine use, some results could be misleading. In the current article we present a case of sexual asphyxia with drug and volatile substance abuse. Toxicological analysis revealed the presence of methamphetamine at a concentration of 1.3μ g/mL in blood. An ethanol-like peak was detected during our routine GC-FID test for alcohol (methylethylketone IS). Subsequent GC-MS analysis identified the peak as ethyl chloride. Levels of 0.05 mg/mL in blood and 0.01 mg/mL in urine were measured. Two facts proved misleading in our case. First: very small difference of 0.027 between the ethyl chloride and ethanol peaks in relative retention times at the GC-FID chromatograms. Second: missing evidence for the use of ethyl chloride at the scene-neither cans of the substance were found, nor such information was available otherwise. Conclusion: there is a substantial risk for mistaking ethyl chloride for ethanol, when ethyl chloride abuse is unanticipated. In the case of slightest uncertainty a GC-MS analysis should be employed to reliably determine the actual substance.