A rapid GC-MS determination of gamma-hydroxybutyrate in saliva

GHB and its related compounds have been known for years in forensic toxicology because of their illicit use in drug-facilitated sexual assault, and to a lesser extent, as party drugs. A sensitive and specific method for the identification and quantification of gamma-hydroxybutyric acid (GHB) in saliva has been developed using gas chromatography-mass spectrometry with selective ion monitoring mode. One microliter of synthetic saliva was spiked with 1.0 μL of GHB-d6 as the internal standard and 1.0 μL of 1,7-heptanediol as a surrogate spike to all samples. After a silyl-derivatization, the sample was injected at a split ratio of 10:1. The following ions were monitoring: 233 and 234 for GHB; 239, 240, and 241 for GHB-d6; and 55, 73, and 97 for 1,7-heptanediol. The limit of quantitation was determined to be 0.5 mg/L with a linear dynamic range of 0.5-50.0 mg/L. Quality control samples (5.0, 20.0, and 30.0 mg/L) were prepared for the evaluation of precision. Analytical precision measured by coefficients of variation ranged from 2.1% to 12.50% in both intraday and day-to-day experiments. Surrogate recovery from saliva samples fell in the range of 94.6% to 100% with an average of 98.37% and a corresponding percent relative standard deviation of 1.2%.