We previously discussed the need for hemp farmers to test their crops and introduced some ideas for in-house testing using chromatography and/or spectroscopy. Herein, I will talk about the pros and cons of the techniques.
Since a spectroscopic data model is based on a primary technique (e.g., chromatography), it can never outperform a well-designed and executed chromatographic method. Also, spectroscopic methods do not have equivalent sensitivities to good chromatographic methods (you can’t measure as low of values). This means that commercially available standards used in chromatography aren’t acceptable for spectroscopy. It also means that spectroscopic instruments might not have the required sensitivity to accurately quantify compliant levels of tetrahydrocannabinol (THC) in hemp products, or, of increasing importance, minor cannabinoids in lower concentrations.
Other challenges facing certain types of spectroscopy include the contribution of O-H (oxygen-hydrogen) bonds from water in the plant, which would overlap with O-H peaks from cannabinoids. Thus, variable levels of moisture in biomass can alter the model’s potency output unless this region of the spectrum is excluded from the model. And, although terpenes might be in lower concentrations in the plant, they’d also add signal to the overall spectrum, especially in terpene-rich products like hashish or concentrates. Thus, spectroscopy might not be as selective.
Much of my career was based in spectroscopy, though, and I know the power of the techniques. They’re fast and non-destructive (except for grinding the biomass to achieve homogeneity) and have little consumables and waste. Although advances in chromatography instruments and columns now enable analyses of 11 cannabinoids in 8 minutes, for example, a spectroscopic method might take a minute or so to get a quick sample screen. You might only get THC and cannabidiol (CBD), though, and with the understandable interest in full-spectrum products, is data on two cannabinoids enough?
Image Credit: Shimadzu
There are no universal data models. You can’t expect a model built with data from lab A to provide equivalent results to lab B. Additionally, models constructed on one parent instrument may not transfer equivalently to downstream “child” instruments. And if a lab’s data doesn’t exhibit strong linearity, the model won’t be relevant. Garbage in, garbage out.
Thus, one opportunity for those interested in spectroscopy could be to purchase a spectrometer from a reputable vendor and build your own model around your own lab data by measuring every sample sent to the lab with your spectrometer first. Companies like Bruker, ThermoFisher, Perkin-Elmer, and Horiba vend solid instruments, and chemometrics packages like CAMO Software’s Unscrambler enable model design.
The tumultuous waters are beginning to relax. Regulations and guidance are within sight. Collectively, we’ll get to where we need to be, but in the interim, hemp farmers have some options to do a little testing on their own to ensure perpetual compliance. And while options are nice, it’s important to recognize that you need an analytical instrument and not a toy.
Image Credit: Mr. Hemp Flower
