Legally regulated synthetic cannabinoids (SCs) are continuously being created by making minor positional modifications to pre-existing analogs; thus, compounds with minor structural differences must be isolated and identified accurately. For iodo-benzoylindole derivatives of SCs, only specific isomers are currently the target of legal control, and it is necessary to establish an analytical method for accurately identifying positional isomers. In this study, we synthesized a series of 57 designer drugs and developed a screening method for identifying halogen positional isomers on the phenyl ring of benzoylindole derivative SCs in serum. Analytical methods using the Discovery F5 pentafluorophenyl column gave the best selectivity and retention of the positional isomer analytes. Some of the meta and para iodo-substituted SCs were eluted at similar retention times and were difficult to separate by liquid chromatography (LC). However, they were identified via the relative abundance of the two product ions in the collision-induced dissociation reaction using LC-hybrid quadrupole/orbitrap high-resolution mass spectrometry. Our synthesized halogen-substituted positional isomer SC library and method for differentiating positional isomers of halogenated benzoylindole SC derivatives could provide an indispensable analysis tool for identifying illegal drugs in serum of drug users.
Keywords: LC-MS/MS; Synthetic cannabinoid; orbitrap; positional isomers; screening library.