Assessment of the role played by n-propanol in distinction of ethanol source in postmortem blood with the assistance of ethyl glucuronide and ethyl sulfate

Abstract

Concentration ratio of ethanol/n-propanol has been employed to distinguish the source of ethanol in postmortem blood, though its reliability remains controversial. Forty-two postmortem human blood samples with ethanol levels in the range of 0.07–4.64 mg/mL were investigated. Ethanol and n-propanol were determined by head-space gas chromatography coupled with flame ionization detection, while ethyl glucuronide (EtG) and ethyl sulfate (EtS) were determined by liquid chromatography–tandem mass spectrometry. EtG and EtS were both negative in 26% of the investigated postmortem blood samples and 11% of n-propanol-negative postmortem samples, indicating that n-propanol was not a reliable marker of putrefaction. It was also found that the ratio of ethanol/n-propanol (supposed to be < 20 without antemortem ethanol consumption) was unreliable by showing great individual differences and was opposite with the result of EtG and EtS in at least 17% of n-propanol-positive postmortem blood samples. Meanwhile, 140 antemortem blood samples were investigated, as an aid to estimate the blood alcohol concentration (BAC) at the time of death for postmortem samples with ethanol both from postmortem formation and antemortem consumption. By comparing with the maximum or minimum value of EtG and EtS concentration under certain BAC in antemortem samples, the BAC range at the moment of death could be estimated in 93% of postmortem samples. The present study proved that n-propanol was not a reliable marker for either putrefaction or ethanol source distinction by showing considerable false rate.