Semi-Quantitative Terpenes by LC/QTOF
After successful implementation of a quantitative cannabinoid HRMS analytical method, the next obvious need was characterization of terpenes. LC/MS is not typically thought of for analysis of volatile compounds but has some advantages over thermally intensive methods such as gas chromatography (GC). The initial work in my laboratory was to simply obtain terpenes response in the MS. This was accomplished through atmospheric pressure chemical ionization (APCI). Again, the common molecular formula pointed to the need for good chromatographic resolution.
Unfortunately, our laboratory equipped our LC/MS with a high-performance liquid chromatography (HPLC) instead of an ultra-performance liquid chromatography (UPLC). There were significant limitations in the resolution of terpenes with a standard HPLC method. As demonstrated for other complex separations, UPLC probably would be a better choice. However, for our research, the partial resolution and semi-quantitative information was sufficient to characterize the samples of interest. We could easily distinguish classes of terpenes (monoterpenes versus sesquiterpenes) and differentiate strains of cannabis. Figure 3 shows an example of terpene standard analysed by HRMS with identification of common terpenes.
Due to potential impact on finished product quality and customer appeal, lipid content of cannabis materials quickly drew the attention of our organization. Our raw material suppliers frequently described a myriad of processes to remove lipids. Lipids were of known concern to our formulators and little was known about what species were present or how effective the removal processes were. For this project, our lab utilized lipidomics (Sciex Lipidview) software and HRMS to create profiles of lipids in cannabis oils. The application was almost exactly that used in biological lipid characterization where an extract is infused into the MS and known parent lipid m/z and fragments are measured. Figure 4 shows the negative ion fatty acid lipid profile of hemp oil. Figure 5 shows the positive ion triacyl glyceride profile of hemp oil. Hemp oil was chosen for development as it would be easy to implement as a long-term control sample.
Our laboratory was successful in providing semi-quantitative values for lipid species and to characterize effectiveness of lipid removal processes. It was speculated this data could be useful in developing IP lipid removal processes and determining if the lipids themselves may have commercial value. Unfortunately, our laboratory wasn’t able to perform widespread characterization of cannabis materials using this technology, but we were able to demonstrate feasibility.
The complexity of the cannabis plant coupled with a diverse emerging commercial market provides significant opportunity for analytical scientists to utilize HRMS beyond contaminate testing. The applications I have described here only serve to highlight the utility of HRMS in this industry.
My hope is contract laboratories and cannabis product development companies can rethink initial capital expenditure in LC/MS to obtain improved return on these investments.
Kris Chupka is the former Director of Analytical Chemistry at Next Frontier Biosciences in Denver, Colorado. Direct correspondence to [email protected].
How to Cite This Article:
Chupka K et al., Cannabis Science and Technology 2(3), 58-61 (2019)