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

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.

Improved measurement of ethyl glucuronide concentrations in hair using UPLCMS/MS for the evaluation of chronic ethanol consumption.

The presence of Ethyl glucuronide (EtG) in hair provides a strong indication of ethanol consumption and its investigation is of interest in both clinical and forensic contexts because of the wide window of detection. However, due to the possibility of false negative results in cases of small ethanol intake or excessive hair washing, the combined measurement of ethyl palmitate (EtP) with EtG could be useful. In this study, a sensitive UHPLC-MS/MS procedure for the measurement of EtG in hair was developed and validated, using optimized sample preparation and chromatographic separation. Milled hair was extracted with water for 24 h at room temperature, followed by clean-up of the extract by ion-exchange solid phase extraction (SPE). Extraction was highly efficient, with yield of 96.93-101.06%. Chromatographic separation was performed with a Fluoro-Phenyl stationary phase. The assay was linear from 4 to 500pgmg-1, with accuracy in the range of 100.30-106.16%. Matrix effects (-0.87 to 5.89%) were adequately compensated by the use of deuterated EtG as internal standard. EtG was measured in hair samples of 46 volunteers, and results were compared with hair concentrations of ethyl palmitate (EtP) and the score in the AUDITC questionnaire. EtG hair concentrations were significantly correlated to the AUDIT-C classification (rs=0.365, p<0.05), but not to EtP hair levels. The diagnostic performance of EtG hair concentrations to identify excessive or moderate ethanol use was similar to the capability of AUDIT-C to identify severe and high health risk (Kappa, p=0.013). The developed assay is suitable for clinical use, providing a useful tool to evaluate chronic ethanol consumption.