Ethyl-glucuronide and ethyl-sulfate in placental and fetal tissues by liquid chromatography coupled with tandem mass spectrometry

The aim of this study was to develop a method for the determination of ethyl-glucuronide (EtG) and ethyl-sulfate (EtS), two direct ethanol metabolites, in early placental and fetal human tissues, as potential biomarkers of transplacental ethanol transfer from the mother to the fetus. Placental and fetal tissue samples were obtained from women undergoing voluntary termination of pregnancy at 12 weeks of gestation. Samples were deproteinized and directly injected into a liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) system. Limits of detection of 13.0 and 23.0 pmol/g and lower limits of quantification of 22.0 and 40.0 pmol/g were reached for EtG and EtS, respectively. Inter- and intraday imprecision and accuracy were always lower than 15%. The method was applied to 70 samples (35 placentas and 35 fetal tissues). Of 35 samples, 4 samples collected from 4 women tested positive for EtG and EtS, always showing higher concentrations for EtG. The placenta/fetal tissue ratio for EtG was 2.9 ± 0.9, whereas EtS showed a ratio of 1.7 ± 0.7. Preliminary results suggest that these metabolites are present in both tissues. Further studies should now corroborate the hypothesis, not yet confirmed, that transplacental transfer of ethanol takes place not only for the parent compound but also for EtG and EtS.