The Matrix Might Be Messing With Those Edibles

Chocolate might hamper efforts to accurately test THC levels in edible cannabis products. It's called "the matrix effect", and it's no joke.


Edible cannabis products are due to be legalized in Canada in October, but how accurate are those potency labels?

All cannabis products are required to have information on the label detailing their tetrahydrocannabinol (THC) content — the psychoactive component in cannabis — but new research from the US suggests that conventional testing methods could be inaccurate.

Experiments with chocolate cannabis products conducted by CW Analytical Laboratories have shown that certain components in chocolate could be skewing test results. Ultimately, this could mean consumers are unwittingly dosing themselves higher or lower than intended.

Consuming too much cannabis in one sitting can have serious side effects: users may experience a rapid heart rate, confusion, anxiety, paranoia, nausea, or even hallucinations and delusions. However, the scale of variability found in these experiments is unlikely to pose a major health hazard for most people, according to lead author David Dawson.

Dawson, whose research was recently presented at an American Chemical Society (ACS) conference, says he’s driven to research potency testing because of the “high stakes” involved for both consumers and businesses.

“If an edible cannabis product tests 10% below the amount on the label, California law states that it must be relabelled, with considerable time and expense,” says Dawson. “But it’s even worse if a product tests 10% or more above the labelled amount — then the entire batch must be destroyed.”

In Canada, labelling inaccuracies in dried flower and oil products have already led to several recalls, an indicator that regulatory oversight is working.

THC may be hiding among the fat content of chocolate

In chemical analysis, the matrix is a term used to describe the other components in the mixture in which the test compound is being analyzed. In this case, the matrix is the chocolate product that cannabis is mixed into. When manufacturers add cannabis, certain components of the matrix may interfere with our ability to test for potency, and this is known as the “matrix effect”.

Dawson and colleagues chose chocolate for their analysis because of how popular it is as an edible cannabis product.

High-performance liquid chromatography, a technique which allows researchers to separate, identify, and quantify the components of a sample, was used as part of the analysis. With the exception of the chocolate, all sample prep conditions remained constant throughout their experiments.

The core finding was that the more product they used in the analysis, the less accurate the results. The team suspects that the THC is binding to the fats in the chocolate matrix.

“When we had less cannabis-infused chocolate in the sample vial, say 1 gram, we got higher THC potencies and more precise values than when we had 2 grams of the same infused chocolate in the vial,” says Dawson. “This goes against what I would consider basic statistical representation of samples, where one would assume that the more sample you have, the more representative it is of the whole.”

Previous research has suggested that chocolate components such as fat, polyphenols, and tannin can directly interfere with extraction and detection procedures.

Dawson noted there is likely an equilibrium coefficient occurring between the solvent and the chocolate during extraction. This is a kind of “push and pull” effect in which the two are competing for the cannabinoids.

Leaving the samples for longer in the solvent was not deemed helpful as the test would simply end up at the endpoint of the equilibrium, but adding more solvent has been touted as an avenue for future research. Similarly, while larger sample sizes would be more representative, the team are currently focused on clarifying whether the effect exists, hence the use of only small sample sizes.

“We’re just establishing this phenomenon at the moment,” says Dawson.

Although accurate testing methods already exist for cannabis products of all sorts, the aim of Dawson’s research is one of refinement: to unearth any minor kinks of which the industry may be unaware, thereby inching us closer to the best method possible. Dawson plans on exploring other matrices in future research including other types of chocolate.

“We owe this research to the scientific community, the producers and the consumers,”  says Dawson. “We have to be able to provide highly accurate and precise testing across a wide swath of matrices.”

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Barry is a journalist, editor, and marketer for several media outlets including HeadStuff, The Media Editor, and Buttonmasher Magazine. He earned his Master of the Arts in Journalism from Dublin City University in 2017 and moved to Toronto to pursue a career in the media. Barry is passionate about communicating and debating culture, science, and politics and their collective global impact.