Liquid chromatographic–mass spectrometric determination of endogenous γ-hydroxybutyrate concentrations in rat brain regions and plasma

A new liquid chromatographic–mass spectrometric (LC–MS) method for determining trace concentrations of γ-hydroxybutyric acid (GHB) in biological samples has been developed. This method utilizes solid-phase extraction for separation, deuterated GHB as an internal standard (IS) and multiple reaction monitoring (MRM) in the negative ion mode to detect the parent and product ions (103 and 57 for GHB, and 109 and 61 for D6-GHB, respectively). The assay produces excellent linearity and reproducibility, with a limit of quantification (LOQ) of about 0.1 μg/ml. The method has been applied for the determination of endogenous GHB in various rat brain regions.