A Quantitative 1H NMR Method for Screening Cannabinoids in CBD Oils
Toxicologically relevant levels of the psychoactive 9 tetrahydocannabinol (9 THC) as well as high levels of non psychoactive cannabinoids potentially occur in CBD (cannabidiol) oils. For consumer protection in the fast growing CBD oil market, facile and rapid quantitative methods to determine the cannabinoid content are crucial. However, the current standard method, i.e. liquid chromatography combined with tandem mass spectrometry (HPLC MS/MS) requires a time consuming multistep sample preparation. In this study, a quantitative nuclear magnetic resonance spectroscopy (qNMR) method for screening cannabinoids in CBD oils was developed. Contrary to the HPLC MS/MS method, this qNMR features a simple sample preparation, i.e. only diluting the CBD oil in deuterochloroform. Pulse length based concentration determination (PULCON) enables a direct quantification using an external standard. The signal intensities of the cannabinoids were enhanced during the NMR spectra acquisition by means of multiple suppression of the triglycerides which are a major component of the CBD oil matrix. The validation confirmed linearity for CBD, cannabinol (CBN) 9 THC and 8 THC in hemp seed oil with sufficient recoveries and precision for screening. Comparing the qNMR results to HPLC MS/MS data for 46 commercial CBD oils verified the qNMR accuracy for 9 THC and CBD, but with higher limits of detection. The developed qNMR method paves the way for increasing the sample throughput as a complementary screening before HPLC MS/MS.