In this study, we describe a rapid gas chromatography-tandem mass spectrometry (GC-MS/MS) analytical method that allows comprehensive detection and structural elucidation of synthetic cathinone-type designer drugs. Our proposed method consists of three simultaneous analytical procedures: 1) selective detection of the carbonyl group characteristic to each cathinone examined via selected reaction monitoring (SRM); and the determination of both 2) iminium cations and 3) substituted benzoyl cations generated via the α-cleavage of their corresponding amines and ketone moieties via product ion scanning, respectively.
One peak was detected in the SRM chromatogram for all cathinones examined in procedure 1), as well as the relevant single peaks in the total ion current chromatograms that resulted from procedures 2) and 3) at the same retention time. SRM of procedure 1) showed the transition of substituted benzoyl cations to substituted phenyl cations due to CO elimination, revealing the presence of carbonyl groups within the structures. Each product ion spectrum of the substituted benzoyl cation allowed for both determination of which group was substituted on the aromatic ring and differentiation between corresponding positional isomers for ethyl, methoxy and methylenedioxy substitution. However, identification of the substitution positions for the methyl, bromine and fluorine groups on the aromatic ring was difficult. On the other hand, differences between structural isomers in the product ion spectra of iminium cations were clearly identifiable, allowing for easy discrimination between isomers.