Elucidation of synthetic N-benzyl cathinone structures using chemical derivatization and liquid chromatography–tandem mass spectrometry analysis

Synthetic cathinones are derivatives of cathinone, the psychoactive ingredient of the khat plant. These β-keto analogs of the corresponding α-methylphenethylamine (amphetamine) are one of the most popular categories of new psychoactive substances (NPSs), which have been widely associated with severe health problems and death by intoxication. One of the most common positions for substitution of the cathinone skeleton is the amine moiety. N-benzylated analogs of cathinones, e.g., 4-methylbenzyl cathinone (benzedrone), and related analogs display limited mass spectral information using liquid chromatography–electrospray ionization tandem mass spectrometry (LC–ESI–MS/MS). In most cases, the spectra of these analogs exhibit only product ions representing the benzyl-containing part, while the important common β-keto phenethylamine skeleton remains unidentified. We present a simple and rapid approach for the unambiguous identification of N-benzylated analogs of various synthetic cathinones based on their chemical derivatization with 2,2,2-trichloro-1,1-dimethylethyl chloroformate (TCDMECF) prior to LC–ESI–MS/MS analysis. The LC–ESI–MS/MS spectra of these cathinone analogs obtained after derivatization provided extensive fragmentation with complete coverage of all parts of the molecule, allowing the elucidation of their detailed structures and identification at a higher degree of certainty. The developed approach was further applied to distinguish and determine the structures of positional isomers of N-benzylated analogs of cathinone, which display identical ESI-MS/MS behaviors.