An Easy Way for the Removal of Residual Hydrocarbon Fractions from Crystallized Cannabigerol and Cannabidiol

In this study we set-up and validated a novel, easy to handle, chemically green, and efficient methodology for the removal of residual hydrocarbon fractions from crystallized cannabigerol and cannabidiol, in turn deriving from the purification and fractionation of hemp-based phytopreparations. The technique described herein is based on the azeotropic distillation of n-pentane, n-hexane and / or n-heptane with H2O in mixtures artificially created by incorporation of this latter to solid cannabidiol and cannabigerol in a fixed ratio (e.g. 10 g of cannabinoids / 0.5 mL distilled H2O), followed by intimate dispersion and mild heat treatment (40 °C) in a rotary evaporator for 30 min under vacuum (50 mmHg). Initial and final percentages of n-pentane, n-hexane, and n-heptane and original and final purity degree of cannabidiol and cannabigerol have been quantified by head space GC/MS and HPLC, respectively. Results from the present study revealed how the residual hydrocarbon fractions decreased by 97.4% (n-pentane), 99.2% (n-hexane), and 98.6% (n-heptane) (n = 6) for cannabidiol and 97.2% (n-pentane), 99.1% (n-hexane), and 99.0% (n-heptane) (n = 6) for cannabigerol. Thus, the method described herein could represent a novel, alternative, easy, and cheapest way for processing cannabinoids from raw hemp material in order to virtually remove all the hydrocarbon solvents used during manufacturing and fractionation procedures. This in turn leads to obtain semi-finished products with high purity and safely compliant with the legal limits regarding the residual content of hydrocarbons. The process set up herein can be considered as a chemically green one since it employs only H2O as the solvent to perform experimental operations and laboratory facilities, like a vacuum pump (even a cheap one like a water vacuum pump) and a rotary evaporator, that are easily accessible to a wide audience. To the best of our knowledge, such an approach is described herein for the first time in the literature.