Ethyl glucuronide and ethyl sulphate determination in serum by liquid chromatography-electrospray tandem mass spectrometry

Background: Ethyl glucuronide (EtG) and ethyl sulphate (EtS) are two ethanol metabolites that can be detected in serum up to 8 It after ethanol elimination. Their presence is therefore indicative of recent ethanol consumption in case of delayed sampling after an event (e.g. car crash).
Methods: A LC-ESI-MS-MS method for the determination of EtG and EtS in serum was developed and validated. Two product ions together with the parent ions were monitored for identification. Pentadeuterated-EtG was used as internal standard.
Results: Excellent linearity for EtG (from 0.22 to 45 mu mol/l) and EtS (from 0.40 to 80 mu mol/1) was observed (r(2) >= 0.9998). LOD and LLOQ were 0.04 and 0.20 mu mol/l for EtG and 0.08 and 0.40 mu mol/l for EtS, respectively. Accuracy (bias) and precision (relative standard deviation), studied at four different quality control levels, were always better than 7%. Matrix effects were found to be negligible. The method was applied to several samples obtained from known alcoholics and social drinkers.
Conclusions: A sensitive and specific determination of EtG and EtS in serum samples was achieved despite a simple and fast sample preparation. To our knowledge, this is the first fully validated method for the simultaneous determination of the two alcohol metabolites in serum