Determination of GHB and its precursors (GBL and 1,4-BD) in dietary supplements through the synthesis of their isotopologues and analysis by GC-MS method

Gamma-hydroxybutyric acid (GHB) and its "pro-drugs", gamma-butyrolactone (GBL) and 1,4 butanediol (1,4-BD), are drugs of abuse with depressant effects on the central nervous system. Many analytical methods have been proposed for the quantitative determination of these compounds mainly in biological matrices but only few have been addressed to dietary supplements and foods Facile synthesis of the GBL and 1,4-BD isotopologues are available by "one pot" Ru-catalyzed homogeneous deuteration of dicarboxylic acids. In this work we propose a new method for determination of GHB, GBL and 1,4-BD in commercially available dietary supplements, based on isotope dilution mass spectrometry (ID-MS). The procedure involves a simple extraction of sample with acidic acetonitrile and direct analysis by GC-ID-MS method without any purification or derivatization. Indeed, the proposed method takes advantage of the complete conversion of GHB (free acid or its salts) to GBL, allowing the quantification of GHB and its pro-drugs. Five levels for each calibration curve have been prepared by diluting working solutions of the analytes to obtain concentrations ranging from 1 to 20 mg/mL. The validation procedures have shown an accuracy between 88 % and 99 % and a precision between 7.3 % and 2.9 % of each analyte in the sample matrix. Positive ions chemical ionization (PICI) have been employed to preserve the information on molecular ions and to improve specificity and sensitivity of quantitative determination.