Ethyl sulfate: a metabolite of ethanol in humans and a potential biomarker of acute alcohol intake.

This study identified ethyl sulfate (EtS) in human urine and compared the excretion characteristics of EtS with that of ethanol and ethyl glucuronide (EtG). Urine samples were collected from healthy subjects after a single ethanol dose, and also selected from routine clinical samples. Simultaneous analysis of EtS and EtG was performed by direct electrospray liquid chromatography-mass spectrometry in the negative ion mode, with selected-ion monitoring of the pseudomolecular ions at m/z 125 for EtS (M(w) 126 g/mol) and m/z 221 for EtG (M(w) 222 g/mol). The identity of EtS in authentic urine specimens was established by co-chromatography with reference substance, the presence of product ions (m/z 97 and 80 from m/z 125) with correct relative intensity, and a correct sulfur isotope ratio for (34)S (m/z 127). After healthy subjects drank ethanol, EtS showed a much longer, dose-dependent elimination half-life than the parent compound. No EtS was detected in urines collected after abstention from ethanol for several days prior to sampling. Among 354 consecutive clinical samples, 86 were positive for both EtS and EtG with a mean EtG/EtS molar ratio of 2.3 (median 1.7). Another three urine samples were only positive for EtS and four only for EtG. The present results confirm that sulfate conjugation is a normal but minor metabolic pathway for ethanol in humans, and EtS a common constituent in the urine after alcohol intake. It is also indicated that the concurrent determination of EtS and EtG will improve sensitivity, when being used as biomarkers of recent drinking.