Rapid screening and quantification of synthetic cannabinoids in herbal products with NMR spectroscopic methods

Abstract

The abuse of “Spice” designer drugs, herbal incenses containing synthetic cannabinoids, has led to an increase in medical incidents and triggered legislations throughout the world banning these harmful designer substances. As more cannabinoids are added to that list, forensic analytical labs are experiencing sample backlogs due to the variety of the products and the addition of new and still-legal compounds. Here we use NMR spectroscopy exclusively to screen for and quantify synthetic cannabinoids in herbal products. In contrast to other qualitative and quantitative NMR methods that have appeared in the literature, in our methods synthetic cannabinoids were directly extracted with NMR solvent without any conventional lengthy isolation, purification or chromatographic separations. ¹H NMR and proton correlation spectroscopy (COSY and TOCSY) were successfully employed to generate molecular fingerprints for synthetic cannabinoids in herbal extracts, taking advantage of the spectroscopic separation power from NMR spectroscopy. The added dimension from the 2D NMR techniques provided additional signals that are easier to differentiate than those acquired by 1D NMR analysis, and valuable correlation signals for screening and comparison. Quantification of cannabinoids by NMR was carried out in d6-acetone solutions with maleic acid as an internal standard, which generated quantitative results that were comparable to our previous HPLC quantification. The overall data suggest that in approximately one hour, NMR spectroscopy can be used exclusively for the non-destructive screening and quantification of synthetic drugs in complex herbal matrices.