Separation, Extraction, and Quantification of R-(-)- and S-(+)-methamphetamine Enantiomers using Chiral UPLC-MS/MS

Methamphetamine exists as two enantiomers: S-(+)- and R-(-)-methamphetamine. The S-(+)- enantiomer is a potent central nervous system (CNS) stimulant and used both pharmaceutically and recreationally. R-(-)-methamphetamine, with lesser known CNS activity, is found in over-the-counter nasal decongestants. Despite their availability, enantiomeric specific quantification is uncommon in toxicology laboratories. This may lead to misinterpretation of the source of methamphetamine exposure. There is increased need for reliable, high-throughput assays for the separation and quantification of these enantiomers in clinical and forensic toxicology.
We report an enantioselective UPLC-MS/MS method for simultaneous separation and quantification of S-(+)- and R-(-)-methamphetamine, along with amphetamine metabolites. Using polysaccharide-based (LUX-AMP) and glycopeptide-based (Chiral-V) columns, we optimized mobile phase composition, column temperature, and elution conditions to balance enantiomeric separation efficiency while remaining cognizant runtime and reproducibility.
Challenges such as peak broadening and reduced column lifetime, common in chiral separations, were addressed through adjustment of mobile phase additives and temperature. Method validation demonstrated excellent calibration model fit for both enantiomers (R² > 0.99), with low limits of detection (LOD) and quantification (LOQ) suitable for biological matrices. The assay also demonstrated robust intra- and inter-day precision, accuracy, and recovery in spiked matrices. This method enables accurate differentiation of methamphetamine enantiomers, with significant implications for criminal justice and public health.