Discrimination between closely related synthetic cannabinoids by GC–Cold–EI–MS

Gas chromatography thermal-electron ionization mass spectrometry (GC–EI–MS) is an established method for the identification of mind-altering substances and is routinely used by forensic laboratories. However, some commonly analyzed drugs of abuse, relating to the synthetic cannabinoids receptor agonist group (SCs), pose a challenge for this conventional technique. As the molecular cation radicals of many excited SCs are labile within the ion source, the relative abundance of the molecular ions obtained by the GC-EI-MS is often too small to allow discrimination of structurally related drugs. In contrast, the cold-electron ionization (cold-EI) method allows the enhancement and clear identification of the molecular ions, while maintaining the ability to compare unknown analytes with comprehensive mass spectrum libraries. This technique was explored for mass-spectrometric identification and unambiguous differentiation of 15 emerging synthetic cannabinoids found on the drug market in Israel and elsewhere. The current method was demonstrated to discriminate pairs of closely related SCs: FUB-PB-22 and FDU-PB-22, and 5F–PB-22 and NM-2201. In addition, the dependence of the molecular ion enhancement on the cold-EI parameters was examined. Finally, analysis of SCs from seized street samples provided by the Israeli police demonstrates the enhanced identification power of GC–cold–EI–MS.