Discrimination of legal and illegal Cannabis spp. according to European legislation using near infrared spectroscopy and chemometrics

Abstract

Aerial parts containing cannabidiol can be purchased in a legal way but cannabis used as recreational drug is illegal in most European countries. Δ9‐tetrahydrocannabinol is one of the main cannabinoids responsible for the psychotropic effect. European Union countries and Switzerland authorize a concentration of THC of 0.2 % and 1.0 % w/w, respectively, for smoking products and industrial hemp. Public health inspectors and law enforcement officers need to check the legality of samples. Therefore there is a need for innovative approaches, allowing quality control of these products in an easy way and preferably on site. In many countries, cultivation of industrial hemp is permitted if the THC content does not exceed 0.2 % w/w. A portable equipment could be a useful measuring tool for farmers to check for the THC content at regular time. In this work, 189 samples were analysed with a benchtop and a handheld NIR device in order to create two classification methods according to European and Swiss laws. All samples were also analysed by GC‐FID to determine their THC concentration. Supervised analysis was applied in order to establish the best model. For the first classification, the accuracy was 91% for the test set with the benchtop data and 93 % for the test set with the handheld data. For the second classification, the accuracies were respectively 91 % and 95 %. The obtained models, hyphenating spectroscopic techniques and chemometrics, enable to discriminate legal and illegal cannabis samples according to European and Swiss laws.

Hyperspectral Imaging With Machine Learning to Differentiate Cultivars, Growth Stages, Flowers, and Leaves of Industrial Hemp (Cannabis sativa L.)

“…Raman measurements, however, require direct contact of samples with the spectrometer to obtain high-quality signals (Sanchez et al, 2020). Duchateau et al (2020) used near-infrared spectroscopy for discriminating legal and illegal hemp, defined by a cut-off concentration of 0.2% THC in European Union countries, obtaining classification accuracies of 91-95%. Crushing dried hemp plants was required prior to the spectroscopic measurements (Duchateau et al, 2020).…”

“…Duchateau et al (2020) used near-infrared spectroscopy for discriminating legal and illegal hemp, defined by a cut-off concentration of 0.2% THC in European Union countries, obtaining classification accuracies of 91-95%. Crushing dried hemp plants was required prior to the spectroscopic measurements (Duchateau et al, 2020). Cirrincione et al (2021) reported on using attenuated total reflectance infrared spectroscopy for the discrimination between fiber-type and drug-type cannabis samples.…”

“…Cirrincione et al (2021) reported on using attenuated total reflectance infrared spectroscopy for the discrimination between fiber-type and drug-type cannabis samples. Spectroscopic sensing, however, only measures small portions of plant tissues and often requires sample treatments (e.g., drying and grinding) (Duchateau et al, 2020) and direct contact between samples and the detector (Sanchez et al, 2020).…”

New perspective for the in-field analysis of cannabis samples using handheld near-infrared spectroscopy: A case study focusing on the determination of Δ9-tetrahydrocannabinol

“…Regarding the application of NIR spectroscopy to cannabis analysis, only a few works can be found in the literature, showing some interesting applications [19][20][21][22]. In a recent work, the possibility of differentiating between legal and illegal cannabis inflorescences by using a qualitative model implemented with a handheld system was explored.…”

Analytical Techniques for Phytocannabinoid Profiling of Cannabis and Cannabis-Based Products—A Comprehensive Review

“…Quantitative data generated by NIR strongly agree with UHPLC-UV data, confirming the potential of employment of NIR spectroscopy in routine monitoring of cannabis plant material and cannabis resins [ 189 ]. Dispersive NIR and FT-NIR methods were developed for quantification of eight different phytocannabinoids (CBDV, Δ 9 -THCV, CBD, CBC, Δ 8 -THC, Δ 9 -THC, CBG and CBN) in ground leaves and inflorescences from C. sativa [ 205 ] and for discriminating illegal and legal cannabis varieties [ 207 ]. A similar NIR method demonstrated sensitivity and specificity for CBD quantification in different liquid pharmaceutical products, thus showcasing its potential as a fast method for monitoring of CBD in the production process [ 206 ].…”