Frontiers in Chemistry (Nov 2022)
Effect of temperature in the degradation of cannabinoids: From a brief residence in the gas chromatography inlet port to a longer period in thermal treatments
Abstract
The substantial increase in legalization and subsequent regulation of cannabis has intensified the control and analytical monitoring of cannabis products to assure sample quality and control the cannabinoid content of the crop. In this sense, the restriction on cultivating legal cannabis plants has been limited to 0.2–0.3% of Δ9-THC content, depending on the host country’s laws. Thereby, cannabis flowers containing more than this limit are considered illicit drug-type cultivations and require the obtention of specific permits to work with them. The official method established by the European Commission set the gas chromatography/flame ionization detector (GC-FID) as the proper instrument to analyze the delta-9 tetrahydrocannabinol (Δ9-THC) content. In the present work, the potential drawbacks associated with the utilization of the official method for the evaluation of the Δ9-THC content have been described. Thus, the effect of the GC injector port temperature in the degradation of cannabinoids was evaluated, observing the degradation of CBD by 20%, generating Δ9-THC and CBN as by-products. Likewise, 17.2% of Δ9-THC was degraded, producing CBN as a by-product. Therefore, despite the brief residence of cannabinoids in the GC inlet, the effect of temperature is noteworthy and must be considered. Derivatization of cannabinoids should be a mandatory step to prevent the thermal degradation of cannabinoids, assuring the accuracy of the results. Furthermore, the evaluation of cannabinoid degradation thermally treated for longer periods of time was carried out. The kinetic degradation of CBD was evaluated in this way, observing a degradation of 0.22 μg/L per second. At the same time, the kinetics of the appearance of Δ9-THC demonstrates the intermediate nature of this cannabinoid, being degraded at 0.03 s−1 μM−1. The degradation of CBD also produced CBN and CBE as by-products.
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