Chocolate skews cannabis potency testing, research reveals

Cannabis-infused edibles have become increasingly prevalent following the legalisation of cannabis in some US states. Cannabis-infused edibles such as gummy bears, cookies and chocolates are proving problematic for scientists trying to analyse their potency and contaminants. New research has revealed that components in chocolate could be interfering with cannabis potency testing, leading to inaccurate results. Results from the research will be presented at the Fall 2019 National Meeting & Exposition, hosted by the American Chemical Society (ACS).

“My research focuses on cannabis potency testing because of the high stakes associated with it,” said David Dawson, PhD, the project’s principal investigator. “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. But it’s even worse if a product tests 10% or more above the labelled amount — then the entire batch must be destroyed,” Dawson said.

By adding cannabis to a variety of products, manufacturers risk affecting the composition, also known as the “matrix”, of the products, thereby impacting potency testing results. Dawson and his colleagues at CW Analytical Laboratories focused on potency testing for cannabis-infused chocolates, as pictured below, because they are a very common product.

Cannabis-infused chocolate presents problems for potency testing. Image credit: Kevin Kerr.

“We also noticed, kind of anecdotally, some weird potency variations depending on how we prepared chocolate samples for testing,” Dawson said. Dawson studied the effects of changing sample prep conditions, such as the amounts of chocolate and solvent, pH and the type of chocolate, on the concentration of Δ9-tetrahydrocannabinol (the main psychoactive ingredient in cannabis). This was measured by high-potency liquid chromatography (HPLC).

Results from Dawson’s research revealed that having less cannabis-infused chocolate in the sample vial, such as one gram, produced a higher THC potency and more precise values than two grams of the same infused chocolate. The results suggested that some other component of the chocolate — a matrix effect — was suppressing the signal for Δ9-THC.

“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,” Dawson said.

“Simply changing how much sample is in the vial could determine whether a sample passes or fails, which could impact the producer of the chocolate bars, as well as the customer who might be under- or overdosing because of this weird quirk of matrix effects,” Dawson said.

Dawson’s team is trying to determine which ingredient in chocolate is causing the matrix effects. Researchers have tried spiking a standard solution of Δ9-THC with different quantities of chocolate bar, cocoa powder, bakers’ chocolate and white chocolate, and observing how the HPLC signal changes in reaction to the different components of chocolate.

“Our best lead right now is that it has something to do with the fats, which makes sense considering that Δ9-THC is fat-soluble,”  Dawson said.

Dawson’s team also intends to extend their research to other cannabinoids, such as cannabidiol (CBD), a non-psychoactive substance found in many edible products. The researchers will also analyse the effect of other food matrices, such as chocolate chip cookies, on the potency of cannabis. The research strives to develop standard methods for cannabis potency testing in a variety of edibles, across a range of matrices.

Image credit: ©stock.adobe.com/au/Eskymaks