Validation of a headspace solid-phase microextraction–GC–MS/MS for the determination of ethyl glucuronide in hair according to forensic guidelines

The analysis of ethyl glucuronide (EtG) in hair is a powerful tool for chronic alcohol abuse control because of the typical wide detection window of the hair matrix and due to the possibility of segmentation, allowing evaluation of alcohol consumption in different periods. Additionally, EtG in hair is often the only diagnostic parameter of choice for alcohol abuse when other clinical parameters such as ALT, AST, γGT and CDT (asialotransferrin and disialotransferrin) are in the normal range and EtG in urine negative. In this paper, we describe the development, optimization and validation of a new method based on hair extraction with water, clean-up by solid phase extraction (SPE), derivatization with heptafluorobutyric anhydride and headspace solid-phase microextraction (HS-SPME) in combination with GC–MS/MS according to forensic guidelines. The assay linearity of EtG was confirmed over the range from 2.8 to 1000 pg/mg hair, with a coefficient of determination (r2) above 0.999. The LLOQ was 2.8 pg/mg and the LLOD was 0.6 pg/mg. An error profile calculated according to the “Guide to the Expression of Uncertainty in Measurement” (GUM) at 99% confidence intervals for the range 5–750 pg/mg hair did not exceed 10%. This range corresponds to more than 98% of the positive samples analysed.