Abstract: Objective To establish the method to analyze γ-hydroxybutyric acid （GHB） and its precursors 1,4-butanediol （1,4-BD） and gamma-butyrolactone （GBL） in urine through LC-MS/MS and provide evidence for related cases. Methods GHB-d6 and MOR-d3 were used as the internal standard. The urine sample was separated by LC after protein precipitation with methanol. The electrospray ion source was for ionization. Each compound was detected through multiple-reaction monitoring （MRM） mode. Results The limits of detection of GHB and its precursors 1,4-BD and GBL were 0.1, 0.1 and 2 μg/mL. The accuracy was 87.6%-98.1%. The intra-day and inter-day precisions were less than 15% and matrix effects were higher than 80%. Conclusion The method is high sensitive, simple, rapid, specific and with high reliability. This study has provided technical support and basic data for forensic cases involving GHB.

Key words: forensic toxicology, chromatography, liquid, tandem mass spectrometry, gamma-hydroxybutyric acid, urine