Indirect chiral separation of crystal methamphetamine seized in Saudi Arabia using GC-MS

Abstract

In the last decade, worldwide illegal production and consumption of methamphetamine (MA) has dramatically increased. MA is chiral and its two enantiomers have different biological properties, the S isomer having higher stimulating and addictive effects and therefore important to determine the enantiomeric ratio in drug seizures. The chiral separation and determination of R and S-MA may be used for characterization of the seized samples and elucidation of the illicit method of preparation. The present article aims to investigate the enantiomeric distribution of R and S methamphetamine in a series of seized samples. The enantioseparation was achieved first by derivatization of MA using L-TPC followed by separation of the resulting diastereomers using GC-MS. The optimized chromatographic method allowed baseline separation of the peaks with a resolution parameter of 2.16. While the total concentration of methamphetamine in the seized samples was between 15.09 and 213.20 mg/g, all investigated samples showed the presence of both R and S enantiomers, with a higher content of S-MA. The enantiomeric excess (ee%) was calculated to characterize each sample, the obtained values were in the range 55.27–92.38%. The results demonstrated that the seized samples originated from different batches and most likely from a stereospecific synthetic route.