Distinction of constitutional isomers of mephedrone by chromatographic and spectrometric methods

Abstract

Many new psychoactive substances (NPS) have similar chemical structures. Separation and unequivocal identification of structural isomers is an important issue due to the fact that they can differ in pharmacology, toxicology, effects and action on the human body, as well as legal status. This paper is aimed at comparing the abilities of different analytical methods (GC-MS, UHPLC-DAD, LC-MS/MS), to distinguish mephedrone and its isomers: 3-MMC, 2-MMC, buphedrone, metamfepramone and ethcathinone. These techniques allowed for distinction between the isomers of mephedrone. In the GC-MS method, combining retention times with the mass spectra made the differentiation efficient. In the UHPLC-DAD conditions, it was impossible to distinguish the isomers based on their retention times, but the UV/VIS spectra were useful in identification. The separation conditions were optimised for the LC-MS/MS method. The identification of isomers was supported by the different intensity of product ions. The LODs for the GC-MS method (1000–2500 ng/mL) in scan mode were definitely the worst. The values for the UHPLC-DAD method were much better (1.4–2.7 ng/mL) making this assay suitable for the analysis of biological material. The LC-MS/MS method was sensitive enough (LODs = 0.03–0.39 ng/mL) for the analysis of biological material even a long time after the initial drug use.

Keywords:

• separation
• identification
• GC-MS
• UHPLC-DAD
• LC-MS/MS