Abstract / Synopsis:
As cannabis legalization gains momentum, an emerging industry has been created that has a need for accurate, reliable and innovative analytical testing. In my role as Director of Analytical Chemistry at Next Frontier Biosciences, I chose high-resolution liquid chromatography/mass spectrometry (LC/MS) to meet these needs. In this article, I will discuss applications in routine testing (potency and contaminants) as well as those more specialized (terpenes, lipids, etc.). Tandem quadrupole/time-of-flight (QTOF) mass spectrometry is shown to be a valuable tool in routine and custom applications that will contribute to the next generation of cannabis products. LC/MS capability in the cannabis laboratory goes well beyond contaminate testing currently used in most cannabis third-party testing labs.
Cannabis legalization has created a new industry for consumer products with recreational and medical applications. The diversity and complexity of products in development rely on thorough and accurate characterization to meet desired end points. Often developers use third-party laboratories to perform this characterization. Mass spectrometry is a key technology for contaminate testing but is often overlooked for other applications. In this article I will recount my time as Director of Analytical for a cannabis biotech company and the high resolution-mass spectrometry (HRMS) applications we developed and used for our research and product development.
Quantitative Cannabinoid Potency by LC/QTOF
In the cannabis industry, the most immediate need for characterization is potency of cannabinoids in flower and concentrates. HRMS was selected as our primary analytical technology, so I initially worked to develop a separation and quantification for cannabinoids.
It’s worth mentioning that HRMS does not provide inherent selectivity for cannabinoids with the same molecular formula. Our scientists evaluated this firsthand and found the differences in MS/MS were too subtle for routine use in quantitation. The necessity for a good LC separation was imperative. Our initial efforts focused on identifying a column stationary phase that had unique selectivity for cannabinoids. The screening process was evaluated by resolution of cannabinoids (CBD), delta-9-tetrahydrocannabinol (Δ9-THC) and delta-8-tetrahydrocannabinol (Δ8-THC) under isocratic conditions. Our laboratory screened more than 10 phases from several manufacturers. Once the phase providing the greatest resolution was identified, we worked on other parameters to obtain a separation of 12 cannabinoids. An example is shown in Figure 1 of the signals for m/z 315.232 and 359.222.
Not long after our separation was established, we found that, for accurate quantitation in the various matrices, there was a need for a relevant internal standard (ISTD). The evolution of ISTD in our laboratory started with deuterated cannabinoids, a paraben, and finally an isoflavone. Unfortunately, we found the purity of the deuterated standards available at the time less than adequate, and the paraben was prolific in the environment.
The quality of cannabinoid standards has improved greatly since that time, so these may be worth re-evaluating. However for our application, the isoflavone worked well. We performed basic validation (accuracy, linearity selectivity) in flower and concentrate and comparison studies with liquid chromatography/ultraviolet detection (LC/UV). The results of our equivalency study are shown in Figure 2.
Our accuracy for cannabinoids was routinely ±10% or better (as monitored by check standards and a control sample). While this may not rival the best LC/UV techniques, we had some inherent advantages with HRMS. The advantages of using HRMS observed were selectivity for cannabinoids versus matrix and the ability to run information-dependent MS/MS scans information dependent acquisition (IDA) in the background for identification of unknown components of interest or verification of compounds identified. The IDA data could be re-evaluated weeks or months after a sample was tested to look for non-target components of interest. Our laboratory analysed hundreds of flower and oil samples with a high degree of confidence in the results.