Enantioselective Analysis of Ketamine and Other Substances Commonly Found in “Pink Cocaine” Preparations via Capillary Electrophoresis and Liquid Chromatography With Ultraviolet Detection

Rising seizures of illicit ketamine-in pure crystalline form and in complex preparations such as pink cocaine-have heightened interest in tracing its origin. As many psychoactive drugs are chiral, knowledge of their enantiomeric composition in seized samples can support source attribution and legal assessment under drug control laws. Enantioselective methods were optimized for five chiral substances commonly found in pink cocaine, namely ketamine, amphetamine, MDMA, tramadol, and mephedrone; the achiral substances 2C-B, lidocaine, and caffeine were also included. Capillary electrophoresis (CE) was performed using sulfated β-cyclodextrin as chiral selector in the run buffer. A CE-UV short-end injection method enabled enantioselective analysis of ketamine in crystalline samples within 4 min (resolution: 6). A CE-UV long-end injection method enabled enantioselective separation of complex mixtures within 17 min (resolution: 2.7-11.1). For high-performance liquid chromatography (HPLC)-UV, a vancomycin-based chiral stationary phase provided resolutions of 1.2-4.7 within 27 min for pink cocaine samples. CE analysis demonstrated superior enantioselectivity, separation efficiency, and shorter analysis times compared to HPLC. However, CE was less robust due to peak area variability and batch-to-batch variation of the sulfated β-cyclodextrin, whereas HPLC allows for reliable quantitation. Of 558 seized ketamine samples analyzed, all but one were racemic, suggesting that (S)-ketamine is currently used mainly in legal pharmaceutical products and is not diverted to the illicit market as large-scale drug substance batches. Nevertheless, chiral analysis should be applied continuously to monitor the market, as the availability of enantiomerically pure drug preparations could lead to future market changes.