Chocolate Can Interfere with Analytical Cannabis Testing

Written by Sabine Downer

Cannabis edibles are hugely popular, and cannabis chocolate is no exception. For the manufacturers that make these edibles, testing is required on the finished product to ensure the product labeling accurately informs consumers. If an edible has more potency than expected, it can result in an uncomfortable experience for the consumer. While cannabis “overdose” is not at all deadly, it is uncomfortable enough that some people will check into a hospital. Or they may not want to try a cannabis product again. Experienced cannabis users may sleep it off, talk themselves down, or take some cannabidiol (CBD) to combat the unexpectedly intense high, but edibles like cannabis chocolate tend to attract a less experienced demographic. This means that it is even more important to ensure label potency is accurate.

Scientists at CW Analytical Laboratories, a cannabis testing lab in Oakland, noticed something funny when testing chocolate cannabis products. When they used a one-gram sample, the tested levels of delta-9-tetrahydrocannabinol (THC) were significantly higher and more accurate than when they used a two-gram sample. This was especially surprising because normally an increase in sample size increases accuracy. The observation seemed to defy traditional statistics and suggested that some component of the chocolate matrix was suppressing signals in the chromatography used to measure potency.

The observation that chocolate and sample size can distort cannabis potency also carries major significance for manufacturers. In California where the lab is based, having more than 10% of the claimed THC potency indicated on the product label means the entire batch will need to be destroyed. If it tests 10% lower that the packaging label, manufacturers have the option to re-label the product. This California cannabis law could be improved, but what’s more important is that the source and reason for chocolate interference gets addressed.

What is unclear is if this lab was utilizing AOAC standards for testing chocolate cannabis edibles, and if this discovery will impact that standard which was established in 2017. The project’s principal investigator, David Dawson, PhD, noted that amounts of chocolate sample, testing solvent, pH, and type of chocolate were all potential factors in the distorted test results.

He is now focusing in on the chocolate matrix itself and discerning which specific chocolate ingredient is causing interference. A follow up study supported the hypothesis that “lipophilic interactions are at the heart of chocolate matrix interference.” [1] Recovery was superior in cocoa powder (less fat) compared to dark and milk chocolate. The relationship is nuanced, however, and requires further investigation.

For more information, please see Dr. Dawson’s article “The Trouble with Measuring Cannabis-Infused Chocolates” available on the Terpenes & Testing website this month.


Image: kwol from Pixabay



  1. Dawson D, Martin R. Investigation of chocolate matrix interference on cannabinoid analytes. Journal of Agricultural and Food Chemistry. 2020;68:5699-5706. doi:10.1021/acs.jafc.0c01161. [Impact Factor: 4.192; Times Cited: 2 (Semantic Scholar)]

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Sabine Downer

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