At the global level, seizures of crystalline methamphetamine (MA) and MA tablets have risen to a new high, indicating that the substance is an imminent threat. MA enantiomer profiling was a useful tool to investigate the prevalence of MA abuse, the intrinsic characteristics of the seized samples and the trends of precursors. In this work, the distribution of enantiomers in clandestine MA crystals and tablets seized mainly in the Yangtze River Delta region, China, from 2008 to 2014 were identified. The MA samples were diluted with internal standard methanol solution, and analyzed by LC–MS-MS. The detection limits of the enantiomers were 0.04 μg/L. The limit of quantification was 0.1 μg/L. As little as 0.2% of the R-enantiomer ratio could be determined. Standard calibration curves of S- and R-MA showed good linearity in the range of 0.1–80 μg/L (r2 > 0.995). All of the seizures were optically pure S-enantiomer in the years 2008 and 2009. Seized samples containing a slight amount of R-MA began to appear in 2010 and increased in the year 2014. No racemic mixture or R-isomer of MA was seized. From this study, we could find out that smuggling routes and/or precursors might be silently changing in the Yangtze River Delta region, China.
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.
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