The analysis of delta-9-tetrahydrocannabinol, cannabidiol and cannabinol in oral fluid and selected commercial products by gas chromatography-mass spectrometry

Abstract

The detection and quantification of cannabinoids within biological matrices are still required, despite the legalisation of cannabis use in South Africa. The development of a fit-for-purpose analytical method for the quantification of cannabinoids in biological matrices other than urine is paramount to accommodate the recent legalisation of cannabis use in South Africa. In this project, a gas chromatography-mass spectrometry method for the detection and quantitation of cannabinoids was developed and validated in aqueous and oral fluid matrices. The behaviour of Δ9-tetrahydrocannabinol and cannabidiol was further characterised in terms of the pre-analytical parameters and a significant difference was illustrated between the two matrices. It was concluded that the more convenient aqueous matrices cannot be used as a substitute for authentic oral fluid during method validations.

The limit of quantitation of 2.0 ± 0.5 ng/mL (at 95% confidence level) for Δ9- tetrahydrocannabinol in oral fluid was lower than the proposed threshold limit of 5 ng/mL instated in other countries. It was concluded that oral fluid has the potential to serve as an alternative matrix to urine when testing for cannabis use but the sampling uncertainty associated with the collection of authentic oral fluid samples has yet to be determined.

Commercially available CBD water- and oil-based products were also analysed with the developed aqueous method and an adapted method, respectively, to determine the prevalence and extent of Δ9-tetrahydrocannabinol contamination and the potential impact on the public. Fourteen of the sixteen CBD products had CBD contents that did not correspond with the product labelling. One of the products contained 125 times the psychoactive dose of 2.5 mg of Δ9- tetrahydrocannabinol and products reported to be “THC-free”, contained up to 152 ± 28 μg of Δ9- tetrahydrocannabinol. All the CBD oils contained cannabinol, which could trigger a positive Δ9- tetrahydrocannabinol screening test. This highlighted that caution should be taken when interpreting cannabinoid screening and confirmation results.