Quantitative analysis of gamma-hydroxybutyrate at endogenous concentrations in hair using liquid chromatography tandem mass spectrometry.

A method capable of quantifying endogenous concentrations of gamma-hydroxybutyrate (GHB) in human head hair was developed and validated using liquid chromatography/mass spectrometry/mass spectrometry (LC/MS/MS). Hair was digested under alkaline conditions, and GHB was isolated using liquid-liquid extraction. LC/MS/MS was performed using atmospheric pressure chemical ionization in the negative mode, multiple reaction monitoring, and deuterated internal standard (GHB-D(6)). Linearity was observed between 0.1 and 100 ng/mg GHB (R(2) = 1.000). The limits of detection and quantitation in human hair were 0.2 and 0.4 ng/mg, respectively. Accuracy at 2 ng/mg and 10 ng/mg was determined to be 97% and 94%, and intra-assay CVs at these concentrations were 5.2% and 7.4% (n = 4). Beta-hydroxybutyrate (BHB), alpha-hydroxybutyrate, gamma-butyrolactone, and 1,4-butanediol did not produce an interference, and there was negligible ion suppression or enhancement from the matrix.