Rapid detection of synthetic cannabinoids in herbal highs using surface-enhanced Raman scattering produced by gold nanoparticle co-aggregation in a wet system

Synthetic cannabinoids (SCs) are a major category of new psychoactive substances that are frequently distributed after addition to plants. To date, various SCs with small differences in their chemical structures have prevailed in the illegal drug market. Thus, the development of a method for rapid detection with high discrimination capability is critically important for the forensic field. Vibrational spectroscopy is a possible analytical technique for this purpose because it can sensitively reflect differences among chemical structures. In this study, we applied surface-enhanced Raman scattering (SERS) with gold nanoparticle co-aggregation in a wet system to plant samples containing SCs. The experimental protocol used was simple and involved only mixing of the sample with several other solutions. It was possible to detect SERS spectra from various stock solutions of SCs by this method. The method was then applied to street samples containing SCs. Some of the plant samples containing SCs did not produce significant SERS signals even though stock solutions of the same SCs did produce SERS spectra. We investigated the reason for this discrepancy and speculated that the solubility in aqueous solutions was a factor determining whether a significant SERS signal could be detected or not. According to this hypothesis, minimal sample pre-treatment methods were applied. This allowed for the detection of SERS spectra from the examined plant samples. The developed approach is a powerful method for screening analysis of SCs in plant fragments.