Cannabis has a long history as a recreational drug and medically as an analgesic and antispasmodic agent. Discovery of the major cannabinoids tetrahydrocannabinol, cannabidiol, and cannabigerol (THC, CBD, and CBG) has resulted in increased interest in their medical effects. While THC is psychoactive and classified as an illicit drug of abuse in most countries, CBD has a legally accepted status in many parts of the world for medicinal purposes. CBD is believed to relieve anxiety and stress and to promote better sleep. Because of the different effects and possible legal consequences, determining the cannabinoid profile of cannabis is of high interest.

Typically, cannabis potency testing is performed by HPLC analysis. While HPLC can detect low concentrations of less abundant cannabinoids, it requires chemical reagents and it is quite time-consuming. This Application Note explains why near-infrared spectroscopy (NIRS) is a superior method for the quantification of THC, CBD, and CBG in dried cannabis because it provides results in less than a minute and does not require any chemicals.

The obtained Vis-NIR spectra (Figure 2) were used to create prediction models for THC, CBD, and CBG content in dried cannabis. To verify the quality of the prediction models, correlation diagrams were created which display a correlation value (R²) between the Vis-NIR prediction and primary method (HPLC) values. The respective figures of merit (FOM) display the expected precision of a prediction during routine analysis (Figures 3–5).