Thermal Degradation of Synthetic Cathinones: Implications for Forensic Toxicology

The synthetic cathinones represent an important class of designer drugs. The widespread attention and publicity associated with these psychostimulants have resulted in numerous legislative actions at state and federal levels throughout the USA. These amphetamine-like compounds are characterized by a β-keto functional group. Although the synthetic cathinones share many properties of their phenethylamine counterparts, the presence of the ketone moiety is responsible for a number of unique and distinct differences in terms of their chemical characteristics and properties. Thermal degradation of methcathinone was first reported several decades ago but has received limited attention. In this study, we identified in situ thermal degradation products for 18 cathinones during gas chromatography-mass spectrometry (GC-MS) analysis. Oxidative degradation arises from the loss of two hydrogens, yielding a characteristic 2 Da mass shift. Degradation products were characterized by prominent iminium base peaks with mass-to-charge ratios 2 Da lower than the parent drug, and in the case of the pyrrolidine-containing cathinones, prominent molecular ions arising from the 2,3-enamine. Chromatographic and mass spectroscopic data are described for 4-ethylmethcathinone, 4-methylethcathinone, buphedrone, butylone, ethcathinone, ethylone, flephedrone, 3,4-methylenedioxy-α-pyrrolidinobutiophenone, 3,4-methylenedioxypyrovalerone, mephedrone, methcathinone, methedrone, methylone, 4-methyl-α-pyrrolidinobutiophenone, naphyrone, pentedrone, pentylone and pyrovalerone. Degradation was minimized by lowering injection temperatures, residence time in the inlet and eliminating active sites during chromatographic analysis. Chromatographic and mass spectral data for the cathinone degradation products are presented and discussed within the context of forensic toxicological analysis, selection of appropriate instrumental methods and implications for the interpretation of results.