Differentiation of ring-substituted regioisomers of cathinone analogs by supercritical fluid chromatography

Various new psychoactive substances, such as cathinone and its analogs, possess similar chemical structures. Accurate identification of structurally similar drugs of abuse is important in forensic drug analysis. Chromatographic differentiation is a powerful analytical technique for this purpose. In this study, we applied supercritical fluid chromatography to differentiate ring-substituted regioisomers of six synthetic cathinone analogs (fluoro-α-pyrrolidinovalerophenone, methyl-α-pyrrolidinovalerophenone, methoxy-α-pyrrolidinovalerophenone, fluoro-α-pyrrolidinooctanophenone, fluoropentedrone, and fluorooctedrone). The examined cathinone analogs were weakly retained on the stationary phase (possessing diol functional group) and eluted quickly. We optimized the conditions to retain the examined cathinone analogs to achieve sufficient separation, and found that the types of functional groups on the stationary phase greatly affected the retention and separation. Systematic examination of the chromatographic conditions showed that the two stationary phases possessing anthracene and pentafluorobenzyl groups had good separation capabilities for the examined 2-, 3-, and 4-regioisomers of six cathinone analogs, which had different skeletal structures. Interestingly, the two stationary phases showed different selectivities, and alteration of the elution order was observed. The developed method was validated and its discrimination ability was investigated by measuring mass spectra and absorption spectra. Supercritical fluid chromatography-ultraviolet absorption spectroscopy/mass spectrometry is a powerful analytical technique for differentiation of ring-substituted cathinone analogs.