Signal-Separated Quantification of γ-Hydroxybutyrate with Liquid Chromatography-Tandem Mass Spectrometry in Human Urine and Serum as an Improvement of the Analyte Adduct Ion-Based Quantification.

Abstract

The aim of the work was the development and validation of a liquid chromatography-tandem mass spectrometry (LC-MS-MS) γ-hydroxybutyrate (GHB) quantification method in urine and human serum by the use of the analyte adduct ion formation strategy. A combined detection with a conventional precursor ion in the negative electrospray mode and additionally GHB adduct ions with both sodium acetate and lithium acetate was in focus. Therefore, GHB quantification was based on separated MS-MS signals. Two tandem mass spectrometers representing different MS-MS generations (Sciex API 4000 QTrap and Sciex API 5500 QTrap) were used for method validation and comparison. Shimadzu HPLC systems equipped with a Luna 5-µm C18 (2) 100 A, 150-mm × 2-mm analytical column were successfully applied for sample analyses. Infusion experiments were performed for adduct identification and analyte detection optimization. Sample preparation could be limited to a simple and fast protein precipitation/sample dilution. An effective signal-separated GHB quantification with three independent precursor ions representing separated areas of the mass spectrum was developed, validated according to forensic guidelines and applied in the routine. The developed and applied strategy resulted in a higher safety factor for the analyte quantification performed in the forensic toxicology. A relevant analytical improvement could be achieved with this alternative adduct-based GHB analysis since a good correlation of analyte concentrations calculated on the basis of separated signals was stated as useful analytical information.