Determination of Gamma-Hydroxybutyric Acid in Urine by Solid Phase Extraction and Gas Chromatography-Mass Spectrometry

Gamma-hydroxybutyric acid has a short half-life in the human body and may be determined at less than 8h in blood and 12h in urine. Consequently, the sensitivity of the instrumentation and the extraction procedure for gamma-hydroxybutyric acid from biological samples are important factors in its determination. In this study, solid-phase extraction was compared to the commonly used liquid-liquid extraction with analysis by gas chromatographymass spectrometry. Solid-phase extraction enhanced the recovery of 0.5, 1.0, 2.5, 5.0, and 10.0mg/L gamma-hydroxybutyric acid. The recovery for gamma-hydroxybutyric acid by solid-phase extraction was 64.5-70.9% compared to 32.6-47.5% by liquid-liquid extraction. Solid-phase extraction also offered shorter analysis time, smaller sample quantities and solvent volumes, and better separation. Solid phase extraction for gamma-hydroxybutyric acid analysis in urine was fully validated and the results were satisfactory. Both extraction methods were used to analyze urine from an individual that was sexually assaulted. Significant differences were observed in the concentrations of the gamma-hydroxybutyric acid with values of 148.07 and 233.15 mu g/mL by liquid-liquid extraction and solid-phase extraction, respectively.