Aspects of cannabis in the laboratory

Abstract

There is a need for accredited methods for determination of the amount of D9-tetrahydrocannabinol (THC) in cannabidiol (CBD) products as a result of a consideration being discussed at the United Nation Narcotics Board in respect to the reclassification of CBD as a narcotic limiting the amount of THC present in CBD products to less than 0.2%-0.3% (w/w). The objective of this study was the development and validation of a simple, rapid and effective High-Performance Liquid Chromatography (HPLC) method for the determination and quantification of THC in CBD oil. The method was divided in two parts: [1] Determination of conditions for extraction of THC from CBD oil and [2] Development and validation of method of analysis to determine THC in CBD oil. The best conditions for extraction of THC from oil were determined by changing three different ratios of solvent to THC in oil (0.3mL MeOH and 0.3mL 5 μg/mL THC in oil, 0.3mL MeOH and 0.6mL 5 μg/mL THC in oil and 0.6mL MeOH and 0.3 mL 5 μg/mL THC in oil), sonication times (15 and 20 minutes), centrifugation force (4500, 6000 and 10000 rpm), time (15 and 25 minutes) and temperature (4ºC and -20ºC). Analysis was conducted using an Agilent 1260 Infinity Series® II HPLC unit with ultra-violet (UV) detection at 220 nm. Separation was carried out on an ACE 5μm C18 Column (250 x 4.6 mm) using a mobile phase composed of acetonitrile and pH 2.5 phosphate buffer (70:30 v/v) at a flow rate of 2 mL/min at temperature of 40ºC using ibuprofen as the internal standard. Areas under the peak (AUP) and retention times (RT) were compared for each scenario. All the runs were carried out in triplicates. The results obtained indicated that the best conditions for extraction of THC from CBD oil were 0.6mL MeOH and 0.3 mL 2.5 μg/mL THC in oil, 20 minutes of sonication, 15 minutes at 6000rpm of centrifugation and two hours at -20ºC. Retention time of Ibuprofen was 2.85 minutes and retention time of THC was 12.72 minutes. The developed method is innovative, quick, and easy to use and can determine THC in oil with good peak shape and resolution. Application of the analytical method will help in the determination of THC in CBD oil for medicinal use.