Discrimination of synthetic cannabinoids in herbal matrices and of cathinone derivatives by portable and laboratory-based Raman spectroscopy

Abstract

One of the greatest challenges for European drug police and customs forces is how to effectively respond to the dynamically changing market for new psychoactive substances (NPS). Due to the NPS phenomenon, there is an increasing demand by customs or drug enforcement organisations for rapid and portable analytical techniques to characterise unknown samples, such as Raman spectroscopy, which are frequently used as first indicative techniques to detect controlled substances like illicit drugs. In this study, the effective discrimination of 28 synthetic cannabinoids and 15 cathinone derivatives using three different Raman spectrometers with different excitation wavelengths (532, 785 and 1064 nm) was investigated. The results show a high comparability of the Raman spectra from different spectrometers using spectral pre-processing methods. A PCA model allows assigning a substance to a specific substance class and additionally provides information on the nature of structural building blocks of the cathinone derivatives or synthetic cannabinoids being in the focus of this study. Characteristic group frequencies for synthetic cannabinoids and cathinone derivatives are summarised in tables to support future identification in other studies and in police and customs forensic case work. Combining both the use of chemometrics and Raman frequency tables has been shown as a successful tool to improve the characterisation of 60 seized herbal mixtures containing synthetic cannabinoids as active ingredients.