Concise analysis of γ-hydroxybutyric acid in beverages and urine by capillary electrophoresis with capacitively coupled contactless conductivity detection using 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid as background electrolyte.

γ-Hydroxybutyric acid (GHB), a neurotransmitter or neuromodulator in the human central nervous system, is often abused in drug-facilitated sexual assaults due to its euphoric and sedative effects. While the analysis of GHB has received continuous attention, its inherent characteristics pose challenges. In the current study, capillary electrophoresis (CE) with capacitively coupled contactless conductivity detection (CD) was built, and Good's buffers were evaluated as the background electrolytes for CE separation and CD detection. On this basis, a simple and efficient CE-CD method was developed for GHB analysis. Through theoretical discussion and experimental optimization, the separation of GHB and related positional isomers α-hydroxybutyric acid (AHB) and β-hydroxybutyric acid (BHB) was achieved within 4 min using 150 mM 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES) as the running buffer. Under the optimized condition, the relative standard deviations of migration time and peak area were less than 1.1% and 4.5%, indicating good precision. The CD signal of GHB showed a good linear relationship with GHB concentration in the range of 3-300 µM with a determination coefficient of 0.9997, and the detection limit was calculated to be 0.37 µM based on the signal-to-noise ratio of three. Furthermore, liquid-liquid extraction (LLE) and solid-phase extraction (SPE) were comparatively studied for sample matrix purification. Combined with the optimized SPE procedure, the developed CE-CD method has been successfully applied for the determination of exogenous GHB in spiked beverages and endogenous GHB in human urine.