An improved method for the analysis of GHB in human hair by liquid chromatography tandem mass spectrometry

The abuse of gamma-hydroxybutyric acid (GHB) and its suspicion in cases of suspected drug-facilitated sexual assault is of keen interest to forensic toxicology laboratories. This paper reports an extraction, separation and detection procedure for GHB in hair utilizing a combination of liquid-liquid extraction and solid-phase extraction using ethyl acetate and Oasis Max(®) cartridge, respectively, after the hair sample was digested. Analysis was by LC-MS-MS using a gradient separation on an Acclaim(®) Trinity(TM) P1 column performing three multiple-reaction monitoring (MRM) transitions each for GHB and its internal standard. The procedure was validated over a range from 0.4 to 50 ng/mg with estimated limit of detection (LOD) of 0.33 and an administratively set limit of quantitation (LOQ) of 1.2 ng/mg. Twenty hair specimens collected from individuals with no known exposure to GHB were analyzed for matrix interferences and to establish initial background levels of GHB. A wide range of endogenous GHB levels were observed in these samples (from less than the LOQ to 4.4 ng/mg). The results suggest the need for additional studies to better establish the full range of endogenous GHB levels in hair and that extreme caution is required in interpreting GHB findings in hair samples.