Abstract
Cannabis sativa L. is widely used as recreational illegal drugs. Illicit Cannabis profiling, comparing seized samples, is challenging due to natural Cannabis heterogeneity. The aim of this study was to use GC–FID and GC–MS herbal fingerprints for intra (within)- and inter (between)-location variability evaluation. This study focused on finding an acceptable threshold to link seized samples. Through Pearson correlation-coefficient calculations between intra-location samples, ‘linked’ thresholds were derived using 95% and 99% confidence limits. False negative (FN) and false positive (FP) error rate calculations, aiming at obtaining the lowest possible FP value, were performed for different data pre-treatments. Fingerprint-alignment parameters were optimized using Automated Correlation-Optimized Warping (ACOW) or Design of Experiments (DoE), which presented similar results. Hence, ACOW data, as reference, showed 54% and 65% FP values (95 and 99% confidence, respectively). An additional fourth root normalization pre-treatment provided the best results for both the GC–FID and GC–MS datasets. For GC–FID, which showed the best improved FP error rate, 54 and 65% FP for the reference data decreased to 24 and 32%, respectively, after fourth root transformation. Cross-validation showed FP values similar as the entire calibration set, indicating the representativeness of the thresholds. A noteworthy improvement in discrimination between seized Cannabis samples could be concluded.
Highlights
The consumption and production of the Cannabis plant (Cannabis sativa L.) is widespread throughout the world [1,2]
This paper has demonstrated the use of a rather large dataset consisting of 97 GC–MS or GC–flame ionization detector (FID) chromatographic fingerprints for Cannabis profiling purposes
To evaluate the effect of the pre-processing, False negative (FN) and false positive (FP) were determined with the aim of minimizing the FP error rate, which resulted in a decreased overlap between the correlation coefficient distributions and an improved differentiation between the seized Cannabis samples
Summary
The consumption and production of the Cannabis plant (Cannabis sativa L.) is widespread throughout the world [1,2]. Interest in this psychoactive plant increased due to the legalization of recreational Cannabis use in some countries [3,4]. In the health care sector, research is rapidly evolving with regard to the medicinal properties of Cannabis [5,6]. In Belgium, this psychodysleptic drug is mainly cultivated indoors and is commonly seized by law enforcement. Despite the high number of seizures in this country, i.e., about 29,000 marijuana confiscations in 2018, and the fact that Cannabis is the most commonly used drug worldwide, research is still lacking with regard to the direct comparison of seized marijuana samples, i.e., Cannabis profiling, for forensic and judicial purposes [8]
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