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Chocolate may be messing with cannabis potency testing, scientists are warning, and it could mean packaged edibles are understating THC content. 

A study published by the American Chemical Society (ACS) found that chemical components in chocolate might be interfering with cannabis potency test results. The findings come from researchers at CW Analytical, a California-based lab founded in 2009 that predominantly tests materials for marijuana growers, manufacturers, and dispensaries, in legal markets. 

CW Analytical focused its research on cannabis-infused chocolates because of the chocolate's popularity as an ingredient in edibles. The study did not disclose the size of the samples.  

“My research focuses on cannabis potency testing because of the high stakes associated with it,” said David Dawson, Ph.D., the study's principal investigator, in a release.

Cannabis-infused chocolate is presenting variants for lab testing THC potency levels, laboratory CW Analyticals found in a recent study. (Kevin Kerr/American Chemical Society)

The results have shown that a component in the chocolate may be suppressing the signal for THC, causing “a matrix effect” in testing. This means the more chocolate in a given test can show a lower THC percentage. This interference is leading to inaccurate results for THC percentages in edibles produced with chocolate.

“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,” Dawson explained. "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.” 

In lab testing, the concentration of THC is measured by what is called high-performance liquid chromatography (HPLC). So what's causing the suppression of THC percentages?

“Our best lead right now is that it has something to do with the fats, which makes sense considering that delta-9-THC is fat-soluble,” Dawson said. The researchers at CW Analytical are trying to determine which components in different types of chocolates — chocolate bars, cocoa powder, baker's chocolate, white chocolate — are causing the HPLC signal changes. “We also noticed, kind of anecdotally, some weird potency variations depending on how we prepared chocolate samples for testing,” he said. Dawson studied the effects of altering sample preparation conditions, such as the amounts of chocolate and solvent, pH, and type of chocolate.

(Photo: Gina Coleman/Weedmaps)

The effects of edible testing inaccuracies cost cannabis business owners time and money.

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

CW Analytics said it hopes to continue its testing and extend analyses to other cannabinoids including cannabidiol (CBD), as well as other foods. This research will be presented at the ACS's fall 2019 National Meeting & Exposition in San Diego. ACS is the world's largest scientific society and its event welcomes thousands of scientific presentations. The Cannabis Chemistry Subdivision has seen growth in membership and attendance to its presentations, a former committee chair told Weedmaps News in April 2019.

Feature image: (Photo: Gina Coleman/Weedmaps)