Investigation of electron ionization mass spectrometric fragmentation pattern of indole- and indazole-type synthetic cannabinoids

A complete database is the key to using mass spectrometry (MS) to identify the structures of organic substances. However, rapid derivation of new psychoactive substances (NPS) has made it difficult for law enforcement agencies in various countries to identify NPS structures using MS. The fragments and cleavage patterns of MS contain much structural information. Therefore, it is possible to overcome the limitations of existing MS databases for NPS structure identification by analyzing the original MS data. This study aimed to investigate the major subclasses of synthetic cannabinoid NPS (SCs) and indole- and indazole-type SCs. A total of 166 indole- and indazole-type SCs were divided into three groups based on differences in the C-3 position. Subsequently, the MS data under the electron ionization source were systematically summarized. Then, a three-step procedure, “core → tail (R₁) → linker and linked group (R₂)”, was established for the structural analysis of indole- and indazole-type SCs. The subclasses were determined using the characteristic fragments F2–F4, which were closely associated with the core, indole, or indazole. Next, the seven types of the tail (R₁) were determined using the mass-to-charge ratios of the six characteristic fragments and F1. Lastly, the 12 combinations of the linker and the linked group (R₂) were identified. Using this procedure, the classes of the core, tail, linker, and linked group in the structures of indole- and indazole-type SCs can be rapidly determined without the limitations of MS databases, thereby laying the foundation for the final determination of the exact structures.