Researchers at the University of Ljubljana and the National Institute of Chemistry in Slovenia have pioneered a new technique that can measure cannabinoid and terpene content simultaneously.
Cannabis contains over 100 unique chemical compounds. When it comes to taste, aroma, and physiological effects, cannabinoids and terpenes are the two most important classes. As a result, testing for these compounds has become standard in the majority of legal markets, including California.
The Typical Approach: Using Two Methods
Cannabis testing labs typically use distinct chromatography methods to measure cannabinoids and terpenes. That’s because cannabinoids and terpenes differ significantly in terms of their polarities, volatilities, and naturally-occurring concentrations.
Terpenes are measured using gas chromatography (GC) while high performance liquid chromatography (HPLC) is increasingly the method of choice for cannabinoids.
A single analytical method to measure both cannabinoids and terpenes could save valuable time and resources, but poses several significant challenges. Other research groups have developed techniques that allow for analysis of both compound groups, but so far nothing has emerged that’s practical for a cannabis testing lab performing routine analysis.
Overcoming Challenges and Developing a Single Method
To find a practical method for quantifying cannabinoids and terpenes simultaneously, the Slovenian researchers started with the challenge of sample prep. Because cannabinoids and terpenes have different polarities and concentrations, each compound group usually requires a different extraction solvent in preparation for analysis.
After testing many solvents, they found acetone yielded the best extraction results. A ratio of 1:17 (300 milligrams of sample to 5 milliliters of solvent) offered good extraction efficiency while providing a high enough concentration of terpenes which are present in much smaller quantities relative to cannabinoids.
Aside from the challenge posed for sample prep, the differing polarities and volatilities of cannabinoids and terpenes allow for robust separation and quantification using GC. However, certain cannabinoids can fail to separate, making quantification nearly impossible. The researchers found that using a more polar stationary phase gave complete separation of all cannabinoid peaks without interfering with the separation of terpene compounds.
Overall, the method provided relatively fast and sensitive analytical performance with good separation of the two major analyte groups in both hemp and high-THC cannabis samples. Validation results confirmed the method’s accuracy and repeatability. The cannabinoid results also closely matched results from a validated HPLC method.
The only downside to the new method is that it uses relatively high temperatures. High temperatures cause cannabinoids to undergo decarboxylation. Therefore the method is not suitable for measuring the difference between acidic and decarboxylated or neutral forms of cannabinoids in a sample.