Enantiomer Profiling of Methamphetamine in White Crystal and Tablet Forms (Ma Old) Using LC–MS-MS

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.