Speaking at The Science of Cannabis Extraction Online Symposium in June 2020, Dr Toby Astill from PerkinElmer, discussed PerkinElmer's recent research on Fourier transform infrared spectroscopy (FT-IR) with Attenuated Total Reflectance (ATR) to provide a quantitative estimation of the decarboxylation reaction progress in cannabis extract.
Abstract: The production of cannabis extracts and oils for medicinal and recreational products has increased significantly in North America. This growth has been driven by both market demand in newly legalized states and patient demand for a greater diversity in cannabis products. Most cannabis extraction processes, independent of solvent or instrument choice, undergo a decarboxylation step whereby the carboxylic acid functional group is removed from the cannabinoids. The decarboxylation reaction converts the naturally occurring acid forms of the cannabinoids, e.g. tetrahydrocannabinolic acid (THCA) and cannabidiolic acid (CBDA), to their more potent neutral forms, e.g. tetrahydrocannabinol (THC) and cannabidiol (CBD). Because the carboxylic acid group is thermally labile, the industry typically applies a heat source, and at times a catalyst, to decarboxylate the cannabinoids.
The heat-promoted decarboxylation reaction has been discussed at length within the industry, but an extensive literature search reveals very few papers on the process. Cannabis quality control laboratory technicians and extraction manufacturing staff have difficulty predicting the optimal reaction time and temperature to attain maximum decarboxylation. Current manufacturing practices typically involve placing the cannabis extract on aluminum sheet trays in a vacuum oven or in a glass beaker on a stirred hot plate. The conditions required for these techniques to reach reaction completion is largely undefined and decarboxylation is rarely monitored during the heating process. The lack of chemical information during this critical processing step leads to a highly subjective determination of reaction completeness. This results in extraction processes that lack scientific robustness and are far less efficient at achieving decarboxylation. Furthermore, the lengthy reaction times coupled with the uncertainty in optimum temperature can result in an inefficient use of laboratory resources and overall lack of process control. To this end, we investigated the use of Fourier transform infrared spectroscopy (FT-IR) with Attenuated Total Reflectance (ATR) to provide a quantitative estimation of the decarboxylation reaction progress in cannabis extract.
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