Comparative study of plastic smoking mixtures containing synthetic cannabinoids using gas chromatography

Abstract

We propose an algorithm for comparative study of plastic smoking mixtures containing synthetic cannabinoids using gas chromatography in the following configuration: a Crystal 5000.2 chromatograph (Russia) with a quartz capillary column (L = 50 m,  = 0.32 mm) with a grafted phase based on polyethylene glycol modified with nitroterephthalic acid and a flame ionization detector. Plastic smoking mixtures (40 samples) seized from illegal circulation by officers of the Transport Department of the Ministry of Internal Affairs of Russia in the Siberian Federal District were used as test samples. Mathematical processing of chromatograms was performed using Chromatek Analytic 2.5 and Unscrambler 11.0 programs. It is shown that profiles of the volatile polar components of the fillers of plastic smoking mixtures containing synthetic cannabinoids are quite well manifested and reproduced, which gives them a very high identification value. To compare the profiles of impurities, 44 target compounds were selected, which provided the best reproducibility of the areas of chromatographic peaks during repeated measurements. The chromatographic peak areas of the target compounds were normalized, and the Pearson correlation coefficients and the Euclidean distances were calculated. A hierarchical clustering of the obtained data was carried out with construction of the dendrograms demonstrating the levels of the similarity of samples from different lots. It is shown that samples could be assigned to a single batch (recipe) if the Euclidean distances between the corresponding profiles do not exceed 0.14, and the Pearson distances — 0.12 rel.u. An algorithm procedure for the comparative study of plastic smoking mixtures containing synthetic cannabinoids using gas chromatography has been developed. This procedure includes profiling of the impurities, selection of the target compounds, normalization of the areas of their chromatographic peaks and subsequent mathematical processing using cluster analysis and calculation of Pearson correlation coefficients and Euclidean distances. The obtained results allow us to recommend the developed procedure for use in expert studies of smoking mixtures containing synthetic cannabinoids.