Full evaporation headspace technique with gas chromatography as a microchemical method for the rapid determination of gamma-hydroxybutyric acid (GHB) in serum samples

Abstract

The misuse of GHB as a knockout agent continues to increase. A full evaporation technique with headspace gas chromatography and flame ionization detection (FET-HS-GC-FID) method has been developed for the rapid determination of GHB (gamma-hydroxybutyric acid; “liquid ecstasy”) in serum samples. GHB occurs as an endogenous substance in low concentrations in mammals, is used as a recreational drug and misused as an agent in drug-facilitated sexual assaults or robbery as “knock out drops” in higher concentrations. Rapid determination of substances is particularly important in emergency analysis, especially in the case of unconscious patients.The FET-HS-GC-FID method developed in this paper operates with a sample volume of only 8 µL serum and provides slightly better validation data than the comparison method, which works with 200 µL serum. In order to be able to detect the low-volatile GHB, this is in situ converted into the high volatile lactone under acidic conditions. A thermostatting time of 20 min at 130 °C is sufficient for the lactonization.The FET-HS-GC-FID method enables the detection of GHB to GBL (gamma-butyrolactone) with a limit of detection (LOD) of 1.25 mg L−1, and a limit of quantification (LOQ) of 4.26 mg L−1 in serum samples. The method shows a good precision intraday (7.2 and 6.4 %) and interday (7.8 and 5.6 %) for both the low (lQC) and the high quality control (hQC) sample and a calibration curve determination coefficient (R2) of 0.999.The comparison of 100 spiked serum samples with GHB show an excellent agreement between the conventional and the new developed FET-HS-GC-FID method with a R2 of 0.984 and the results of the proficiency tests showed a very good agreement with the target values and were in all cases within the assessment limits.