Challenges of cannabidiol determination in emulsified cosmetics and application of solid-phase extraction followed by HPLC-UV-MS/MS.

The recent surge in popularity of cannabidiol-infused products extends beyond food and supplements to the cosmetic industry. Accurate labeling remains a significant concern, as many products fail to meet advertised cannabidiol content and/or contain psychoactive tetrahydrocannabinol above the permissible levels. In this work, we present the use of an HPLC-UV-MS/MS method for the quantification of five major cannabinoids (cannabidiol, cannabidiolic acid, tetrahydrocannabinol, tetrahydrocannabinolic acid, and cannabigerol) in oil-in-water cosmetic emulsions. The sample extraction is based on dispersing the sample in isopropanol, followed by solid-phase extraction using Bond Elut Plexa PAX cartridge. The viability of this method is demonstrated by comparing matrix effects in samples subjected to solid-phase extraction (0‒11% suppression of cannabidiol ionization) to samples extracted without additional purification steps (0‒84% ionization suppression of cannabidiol ionization). The limit of quantification is determined at 0.1 mg/g and the calibration is employed in the range of 0.1‒50 mg/g for cannabidiol and 0.1‒10 mg/g for all other analytes. Finally, 36 real cosmetic samples from the Czech market were analyzed. Of these, 14 indicated the amount of CBD on the label but only five (36%) were accurate, i.e., within 90‒110% of the labeled amount, and a considerable amount of THC (0.16 ± 0.01 mg/g) was found in one sample. These findings contribute to the cumulating evidence that cannabidiol-based consumer products are often mislabeled and highlight the importance of better regulatory compliance.