Regioisomer Differentiation of Ring-Substituted Chloromethcathinones and Bromomethcathinones Using Gas Chromatography/Electron Ionization-Triple Quadrupole Energy-Resolved Mass Spectrometry

Abstract

Positional isomers o-, m-, and p-chloromethcathinones (CMCs) and m- and p-bromomethcathinones (BMCs) were effectively differentiated using gas chromatography (GC) and energy-resolved mass spectrometry (ERMS) analyses. GC demonstrated that the free bases of CMC and BMC isomers were simultaneously baseline-separated at a slow column heating rate (5 °C/min) using a conventional low-polar capillary column. ERMS showed that the trifluoroacetyl derivatives of the positional isomers differed in mass spectral abundances of both halophenyl and halobenzoyl cations. Moreover, the logarithmic plots of the abundance ratio of the two cations as a function of the collision energy (CE) exhibited marked differences among the isomers at each CE, following the order of ortho < para < meta for CMCs and para < meta for BMCs. The performed theoretical calculations of dissociation energy agreed well with the ERMS measurements. The GC and ERMS methodologies enabled unambiguous and reliable differentiation of CMC and BMC isomers. The developed approach is expected to significantly contribute to the accurate structural identification of new psychoactive substances in forensic, toxicological, and clinical fields.

Discrimination and quantitation of halobenzoic acid positional isomers upon Th(iv) coordination by mass spectrometry

“…Ion mobility-MS is preferable for distinguishing large isomers with different shapes, sizes and collision cross sections such as peptides, 7 glycans, 8 lipids 9 and metabolites, 10 etc. Isomer discrimination by tandem MS is based on the gas-phase unimolecular fragmentation patterns 11–14 or reaction tendencies with metal ions, 15–17 which is applicable for small molecules. For the discrimination of XBA positional isomers, it is known that o -FBA (fluorobenzoic acid) is distinguishable from m -, p -FBA using solid-phase extraction coupled with ion chromatography–MS and o -CBA (chlorobenzoic acid) is distinguishable from m -, p -CBA using gas chromatography–MS due to the differences in retention time.…”

Influence of Metal Coordination on the Gas-Phase Chemistry of the Positional Isomers of Fluorobenzoate Complexes

“…Isomer discrimination is of significant importance and well-acknowledged to be a challenging problem. Direct mass spectrometry (MS)-based methods, albeit with the merits of sensitivity and efficiency, are generally not suitable for this purpose because of the identical mass of the isomers, but it is possible to overcome such obstacles with the aid of liquid and gas chromatography, − ion mobility spectrometry, − and ultraviolet as well as infrared spectroscopy. − Additionally, tandem MS has evolved as another crucial means for isomer discrimination on the basis of the diagnostic ratio of fragment ions. − …”