Supercritical fluid extraction of cannabinoids

In-house extractions were performed with 10–15 g of ground cannabis plant material from NIDA. Weighed samples were placed in 25-mL stainless steel extraction vessels, and a Waters MV-10 ASFE supercritical extractor system controlled by ChromScope^® software was used for supercritical CO₂ (>99.99% purity) extraction without the addition of modifiers. The CO₂ flow rate was 2.0 mL/min at 57°C with a controlled pressure of 25 MPa. Absolute ethanol at a flow rate of 4.0 mL/min was used to elute the extracted materials. The optimal extraction time was determined to be 3 h. Extracted cannabinoids were concentrated using a rotary evaporator mounted in a 57°C water bath. After ethanol removal, the concentrated cannabis extract was either analyzed directly or incubated at 110°C for varying times to evaluate the level of decarboxylation of the cannabinoid acids. These extracts were used in HPLC-PDA method development.