An Optimized Solid-Phase Microextraction and Gas Chromatography–Mass Spectrometry Assay for the Determination of Ethyl Palmitate in Hair

Abstract The use of hair as a matrix for the evaluation of chronic ethanol drinking behavior presents the advantage of a longer window of detection and higher specificity when compared to classical biochemical markers. The most recent recommendations the Society of Hair Testing (SOHT) indicate that ethyl palmitate (EtP) hair levels can be used to estimate the ethanol drinking behavior, alternatively to the combined measurement of four main fatty acid ethyl esters. In this study, solid-phase microextraction (SPME) conditions for the extraction of EtP from hair were optimized using response surface analysis, after a Box–Behnken experiment. Analyses were performed by GC-MS. The optimized HS-SPME conditions, using a PDMS-DVB (65 μm) fiber, were pre-adsorption time of 6 min, extraction time of 60 min and incubation temperature of 94°C. The linear range was 0.05 to 3 ng mg−1, with accuracy within 95.15–109.91%. Between-assay and within-assay precision were 8.58–12.53 and 6.12–6.82%, respectively. The extraction yield was 61.3–71.9%. The assay was applied to hair specimens obtained from 46 volunteers, all presenting EtP levels within the linear range of the assay. Using a statistically designed experiment, a sensitive SPME-GC-MS assay for the measurement of EtP in hair was developed and validated, requiring only 20 mg of hair.