Published: Journal of Analytical Toxicology, ISSN 0146-4760, Volume 27, Number 7, October 2003, pp. 445-448

Stability of Plasma Gamma-Hydroxybutyrate Determined by Gas Chromatography–Positive Ion Chemical Ionization-Mass Spectrometry
Meng Chen, David M. Andrenyak, David E. Moody, and Rodger L. Foltz
Center for Human Toxicology, Department of Pharmacology and Toxicology, University of Utah, Salt Lake City, Utah 84112

An effective method for the determination of gamma-hydroxybutyric acid (GHB) in human plasma is described that utilizes a simple liquid–liquid extraction procedure and gas chromatography–positive ion chemical ionization-mass spectrometry (GC–PCI-MS). The method has been used to study the stability of plasma GHB under several storage conditions. Following the extraction with acetonitrile, GHB and deuterated GHB (GHB-d6) were derivatized with N,O-bis[trimethylsilyl] trifluoroacetamide (BSFTA). After the separation on a capillary GC column, the derivatives were ionized with ammonia reagent gas and analyzed by MS. The lower limit of quantitation in 100 µL of plasma was 2.5 µg/mL, over a range from 2.5 to 250 µg/mL. The coefficients of variation did not exceed 3.9% and the mean measured concentrations did not deviate more than 8% from the target for both intra- and interassay precision and accuracy. Plasma GHB was found to be stable at –20°C for up to 9 months, at room temperature for 48 h, and after 3 freeze/thaw cycles. It was also found to be stable in processed samples stored at room temperature for 5 days and for 15 days at –20°C.

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