An efficient HPLC-UV method for determination of tetrahydrocannabinol in oil

Abstract

Objective: The purpose of this work was to develop and validate a high-performance liquid chromatography (HPLC) with ultra-violet (UV) detection method for the determination of ∆9-tetrahydrocannabinol (THC) in oil. Methods: HPLC analysis was carried out using an Agilent 1260 Infinity Series® II liquid chromatography system with ultra-violet detection. The stationary phase consisted of an ACE 5 μm C18 column 5 μm (250×4.6 mm) at a temperature of 40°C. The mobile phase consisted of acetonitrile and phosphate buffer (pH=2.5) (70:30, v/v) at a flow rate of 2 mL/min. The injection volume was 20 μL. The UV detector was set at 220 nm. Separation of THC from oil was carried outusing solvent extraction: 0.6 mL of methanol, 0.3 mL of THC in oil and two drops of internal standard were placed in a centrifuge tube, vortex mixed for 30 s, sonicated for 20 min, and centrifuged at 6000 rpm for 15 min. The organic layer was separated, stored at −20°C for 2 h, and centrifuged at 6000 rpm for 15 min. The organic layer was separated again, passed through syringe filters of 0.45 μm, and analyzed. Results: The method was found to be linear in the range of 0.039–5.000 μg/mL, with acceptable inter- and intra-assay precision, accuracy, and stability. The limit of detection was 0.019 μg/mL and the limit of quantification was 0.039 μg/mL. Conclusion: The developed method is 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.