Applications of ion mobility spectrometry (IMS) to the analysis of gamma-hydroxybutyrate and gamma-hydroxyvalerate in toxicological matrices

Abstract

The predator drug gamma-hydroxybutyrate (GHB) and its lactone form gamma-butyrolactone (GBL) continue to present significant analytical challenges to forensic toxicologists and chemists. The five-carbon analogue (gamma hydroxyvalerate GHV) and the corresponding lactone GVL) are emerging as substitutes for GHB, adding further complications. Ion mobility spectrometry (IMS) was investigated as a method of screening urine and breath for the presence of these drugs and their degradation products. Sample was introduced into the instrument via a programmable split/splitless injection port with thermal desorption. The injection method in effect replaces problematic solvent extraction methods with a physical extraction, an efficient method in the present case considering the hydrophilic nature of GHB. No chromatography was employed and results were obtained within a few seconds. The negative ion mode showed the greatest sensitivity with detection limits in the low parts-per-million range for GHB and GHV. Because GHB is often delivered in alcoholic beverages, ethanol and acetaldehyde, along with potential interfering compounds methanol, isopropanol, and acetone, were also analyzed. None were found to interfere. The thermally induced ring opening prevented differentiation of GHB and GBL using direct injection/thermal desorption protocol, but IMS does show promise as a rapid, simple, and affordable screening technique for GHB and related compounds.