Chiral separation and determination of R/S-methamphetamine and its metabolite R/S-amphetamine in urine using LC-MS/MS

Methamphetamine (MA) and amphetamine (AM) are widely abused drugs. Differentiation of MA and/or AM abuse from therapeutic ingestion of MA and/or AM or one of their precursor drugs is therefore of relevance in clinical and forensic toxicology. The aim of the study was to develop a simple, rapid, and accurate method for the chiral separation and determination of R/S-MA and R/S-AM in urine using liquid chromatography electrospray ionization tandem mass spectrometry operating in the positive ion multiple-reaction monitoring (MRM) mode. 20 μL of urine was diluted 500 times and 20 μL was injected. The chromatographic system consisted of a Chirobiotic™ V2 column (2.1 mm × 250 mm, 5 μm), and the mobile phase was methanol containing 0.1% (v/v) glacial acetic acid and 0.02% (v/v) ammonium hydroxide. The method was fully validated through assessments of its linearity (0.05-50.00 mg/L, r(2)>0.994 for all analytes), and LOQ (0.05 mg/L for all analytes). No matrix effect was observed. The method was successfully applied to 86 urine samples from suspected MA abusers. Only the S-isomers of MA and AM were detected in 72 samples. The concentrations of R-MA ranged from below the LOQ to 13.76 mg/L in 14 urine samples with both enantiomers of MA and/or AM. Pure S-MA is the most common found analyte in urine and principally used by abusers.