Development of LC-MS/MS and GC-MS/MS Methods for the Detection of Ethyl Glucuronide (EtG) and Ethyl Palmitate (EtPa) in Hair

Alcohol abuse is a widespread addiction globally, leading to long-term health issues and social consequences. Ethyl glucuronide (EtG) and ethyl palmitate (EtPa) are frequently requested by local authorities, solicitors, or private individuals to assess long-term chronic excessive alcohol consumption. In this paper, we present a validation process aimed at developing sensitive methods for detecting EtG and EtPa in hair samples. EtG was extracted by overnight sonication in water followed by sample clean-up using solid phase extraction (SPE) and analysis by liquid chromatography-tandem mass spectrometry (LC-MS/MS). EtPa was extracted using a simple ultrasonication extraction followed by analysis using gas chromatography-tandem mass spectrometry (GC-MS/MS). The analytical method was validated by assessing linearity, precision, accuracy, recovery, sensitivity, and selectivity. Both EtG and EtPa methods obtained a coefficient of determination (r2) above 0.999 across concentration ranges of 4, 8, 16, 24, 48, and 96 pg/mg and 120, 240, 360, 480, 600, and 720 pg/mg. Extraction recoveries were both close to 100% with stable retention times and proven sensitivity and selectivity. These methods were validated according to the standards set by the United Kingdom Accreditation Service (UKAS) Lab51 and ISO 17025.