Cataloguing Cannabis Chemistry’s Hidden Figures: A Q&A With Jerry King

With over 55 years of experience in chemical engineering, Dr Jerry King’s understanding of supercritical CO2 is older than most of the extractors that use it. Since 2013, he’s offered that experience up to the cannabis industry, and is now heading a new research project to catalogue and determine the crucial cannabis chemical data the industry has been missing.

Ahead of his presentation at the cannabis science conference Emerald Scientific in February, he told Analytical Cannabis what the project means for cannabis extraction.

Leo Bear-McGuinness (LBM): You’ve been in the field of supercritical fluids for some time. Can you explain how you transitioned into cannabis research?

Jerry King (JK): Yes, I can. I'm a bit of an older gentleman, and in 2012, after retiring from an academic post at the University of Arkansas, people started contacting me from the cannabis community regarding CO2 extraction, which I've had considerable experience in. I realized there was a synchrony between what I had been doing and this technology applied as a preferred method of extraction. So that's what got me linked up with a cannabis and the hemp people. And I should comment that my PhD is in analytical chemistry. So, I also wear a hat involving extraction. But my primary connection is in processing and extracting cannabis concentrates.

LBM: Your presentation at Emerald Scientific Conference will center on physical chemical data. Can you explain the importance of these data to the cannabis industry?

JK: Yes, I can. I became concerned a couple of years ago, in both chemistry and chemical engineering in the cannabis area, that there was a lack of data of physical properties. Put simply, all the way from values which are approximate for the boiling points and melting points, to boiling [and] melting points under vacuum, which is used in vacuum distillation to purify cannabis extracts and concentrates. And it became very apparent from examining shipping documents and health and safety data that this data was sorely missing and needed. And that given some of the prohibition in research institutes, academia, even government agencies, that something had to be done – at least, a plea made for studies and, also, predictive methods.

So, I sort of embarked over the last couple of years in gathering this data together, hence the term data mining, and was able to come up with some useful information but also voids in our knowledge base. And this not only included the individual cannabinoids, like THC and CBD, but also the terpenes that are important in the entourage effect, which frequently overlap with property databases for essential oils. So, that is the focus of my talk, to relay what I have found, and to offer methods.

LBM: So, these kinds of figures, evaporation points at certain temperatures in certain conditions etc., they’re missing from cannabis labs?

JK: Yeah, that is what I found in general, as well as simple things like melting point and boiling point. I recently purchased a kilo of CBD and the [company] sent along data sheets with it. And on all the things, including things like flammability index, there was no information. I don't think the company did its homework. But I felt like this is the state of the industry right now. We need this. And as this industry scales up, despite whatever technique of extraction or processing would be applied, there's a need for this data to do modelling. I'm connected with some teams in Canada in an academic institution, where we're modelling these things such as the ethanol extraction applied to hemp and CBD content, and it's very much of a struggle in working with the student teams to provide them with the data because it doesn't exist.

LBM: Now I suppose this question has a very obvious answer, but why is this information missing? Is it simply down to the history of prohibition of the substance?

JK: I think that plays a role in it because I also did, early last year, nine weeks in New Zealand with a quasi-government agency, and I became aware that similar problems exist in the USA, Canada, and even down under in New Zealand. And again, I think it's reservation. When you work in a laboratory, even if it's analytical analysis, it's quite arduous to work with any appreciable quantity of cannabinoids. And you need flexibility in determining these properties and even moving the target chemicals from one lab to another to determine physical data is a major of roadblock. This paranoia we seem to have with regards to cannabis historically.

LBM: How have you sourced these data figures? Through experimentation?

JK: I hope to get to some of that. But most of this is being done by gleaning from the literature. This can go all the way from a simple Google search to scientific literature databases. And I do this extensively. So that's primarily where it's coming [from]. And as I say, I've accumulated this over time, since really embarking on this journey into the cannabis technology area, which was about 2013.

LBM: Fantastic. Good paperwork’s rarely appreciated. What would be the great advantage for a cannabis researcher in having these figures?

JK: Well, one would be which extraction solvent to utilize. For example, ethanol is being touted as a solution to the large-scale processing of CBD from hemp. It's not quite as simple as it may sound and there has evolved very quickly a number of techniques using different temperatures of ethanol to extract, because one of the issues with any extraction method in the cannabis area is the extraction of unwanted components, such as waxes, lipids, colour bodies, frequently referred to as chlorophyll. This can be done almost on a semi-automatic basis by using ethanol at various temperatures, ranging all the way from ambient to temperatures as low as minus 80 or liquid nitrogen cooling type temperatures.

As an example, there is no solubility data. To be candid, there is no solubility data that I've been able to uncover on the solubility of CBD in ethanol at 20 or 25 degrees centigrade. And that's a bit disturbing because whether you're an extractor or you’re a formulator making tinctures, that information would be  essential. And, in terms of the sub-ambient processing, there is no temperature-dependent solubility of ethanol at lower temperatures or the compounds you're trying to remove.

I have done some calculations on terpenes. And the revealing thing about this data mining approach is that terpenes really have no affinity for ethanol. So, I think this physical data that I'm attempting to describe is critical. Just in case I've examined, CBD solubility in ethanol, there just is absolutely nothing out there in data that, at least, is publicly available.

LBM: So, these figures have been missing for so long, while so many extractions have taken place. That’s quite shocking.

JK: Yeah, it is. When people are selling equipment into this industry, are they really giving you the accurate description of it? Do they really understand it?

LBM: So, following your presentation at the Emerald conference, how does this research continue? Will the research institute in Canada progress to experiments?

JK: My hope is that I will collaborate with him on site in Canada, perhaps to determine some of these properties. I'm hopeful of setting up some experiments but in collaboration with someone. We do have other sources of agencies. There is one here in the United States called NIST, the National Institutes of Science and Technology. I am aware of some work done at Boulder, Colorado laboratories on determining vapour pressures as CBD and THC, not under vacuum but at more ambient conditions. So, you know, this is a nice little segment of data that would certainly be welcome. But I believe it is these kinds of agencies, the standards agencies in our federal government, that need to step up, and, of course, academia also.

We do have a number of professional organisations that are stepping forth, particularly in the analytical method development area. Much of this was left to the cannabis community to develop themselves. Now, we see more and more standardizing agencies involved in it, such as the Association of Official Analytical Chemists (AOAC), another standards testing institute, the American Standards and Testing Materials (ASTM). The American Chemical Society now has a cannabis chemistry subdivision that is quite dynamic. This gives you a flavour for some of these organizations that are developing standardized methods for our industry.

This article originally appeared in Analytical Cannabis' Advances in Cannabis Extraction and Processing ebook in March 2020.