Direct determination of the ethanol metabolites ethyl glucuronide and ethyl sulfate in urine by liquid chromatography/electrospray tandem mass spectrometry

A liquid chromatography/electrospray tandem mass spectrometry (LC/ESI-MS/MS) method for the determination in urine samples of two ethanol metabolites, ethyl glucuronide (EtG) and ethyl sulfate (EtS), was developed and validated. Pentadeuterated EtG was used as internal standard for both EtG and EtS. In addition to the surviving ions, two MS/MS reactions were monitored for each analyte, with the deprotonated molecule as precursor ion: m/z 221 --> 75, m/z 221 --> 85 (EtG), and m/z 125 --> 97, m/z 125 --> 80 (EtS). Sample pretreatment, though very simple and rapid (1:50 water dilution and centrifugation of 50 muL of urine), was found to contain the occurrence of matrix effects. The method was accurate and precise over the linear dynamic range (0.05-10 mg/L). The analytes were stable in frozen urine for at least 1 month. The assay was applied to several authentic urine samples from social drinkers and to alcoholic beverages.