An LC-MS/MS method for comparing the stability of ethanol's non-oxidative metabolites in dried blood spots during 90 days.

Problems of stability were found for biomarkers of alcohol consumption, ethyl glucuronide (EtG), ethyl sulfate (EtS), phosphatidylethanols (PEths) and fatty acid ethyl esters (FAEEs) in whole blood. The purpose of this study was to establish a method for the determination of these 4 kinds of ethanol's non-oxidative metabolites in dried blood spots (DBS) by liquid chromatography tandem mass spectrometry (LC-MS/MS), and to evaluate their stability. In this method, 50 μL of human blood was spotted on a filter paper for DBS analysis. Samples were extracted by methanol, reconstituted by 2-propanol and injected in the LC-MS/MS system. Limits of detection were among 0.5 - 50 ng/mL, deviations in accuracy and precision were all lower than 15% at three quality control levels. The stability of the 4 kinds of ethanol non-oxidative metabolites in DBS was investigated during a 90-day range under 3 temperatures, -20 °C, 4 °C and 25 °C. EtG and EtS showed a high level of stability in DBS in the 90-day range, regardless of the temperature. FAEEs was unstable in 3 days. PEths showed a stability within 15 days in postmortem DBS and 60 days in antemortem DBS respectively at all temperatures.