Ethyl glucuronide in nails: method validation, influence of decontamination and pulverization, and particle size evaluation

Ethyl glucuronide (EtG), a minor metabolite of alcohol, is present in hair and nails, and thus can be used as a maker to estimate previous alcohol consumption. Due to the low concentrations of EtG in keratinized matrices (pg/mg range), sensitive analytical methods and optimized sample preparation procedures are essential. While several methods for the detection of EtG in hair have been published, its detection in nails has been scarcely investigated. In this study, an analytical method for the determination of EtG in nails using gas chromatography coupled with tandem mass spectrometry (GC–MS/MS) was developed and validated. In addition, the influence of sample preparation on EtG concentrations was evaluated. The calibration curve was linear from 2 to 100 pg/mg, and the lower limit of quantification (LLOQ) was 2 pg/mg. The method was applied to finger- and toenails of five regular alcohol consumers, with concentrations ranging from <LLOQ to 123 pg/mg. No significant difference in EtG concentrations in washing solutions was found with the use of different decontamination procedures, including hexane, dichloromethane, methanol, acetone, and water as solvents. More intense pulverization of the nail samples increased EtG concentrations, in parallel with a decrease in particle size, but reaching a plateau. In conclusion, we present a sensitive, validated GC–MS/MS technique for the determination of EtG in nails which were pulverized to obtain a high extraction surface area.