What are the challenges faced by analytical labs working with edibles?
Measuring the chemical contents of edible products has historically been a challenge to the cannabis industry, though it is unclear to what extent that challenge is separate from the overarching accuracy problem of cannabinoid and terpene content labeling in the industry itself. 
To give some context to the problem, let’s review a recent study published by the Journal of the American Medical Society (JAMA) regarding cannabinoid (mis)-labeling in edible medical cannabis products.  Dr. Ryan Vandrey of Johns Hopkins School of Medicine looked at 75 products from 47 separate brands purchased at medical dispensaries from across the West coast, including baked goods, beverages, and chocolate/candy. Their criteria for selection included those items with a specifically-stated cannabinoid content level.
The results, simply put, were shocking. Only 17% (13 items) of edibles tested were “accurately” labeled, meaning that the sample results fell within a generous +/- 10% range of the stated THC content. Baked goods had by far the lowest levels of accuracy (<10% of products), followed by candies/chocolate (20%) and beverages (~25%). 
The problems shown manifested in extremes at both ends of the spectrum. On the one hand, of the 60% of products that were over labeled (meaning they had less THC in them than the label said), some had a THC content equivalent of less than 1 mg for the entire package… basically meaning, they had no THC in them. On the other hand, some of the 23 products that were under labeled (more THC than it said), the dosage exceeded six times the stated amount.  Unaware of these differences, consumers could be under-dosing their medication… or be in for one hell of a ride.
These dosage deviations represent an outstanding safety concern, as a national regulatory system that ensures accurate reporting and dosing does not yet exist. Gross mislabeling of cannabinoid content has also triggered warning letters to businesses from the FDA in the past. And frankly, no one out there wants to have to worry about the accuracy of cannabinoid label contents.
Chemical content labels are in arguably one of the best results of legalizing the cannabis trade, as you are no longer left to wonder or worry what you’re ingesting or at the mercy of your dealer or friend. So, as a manufacturer, do your consumers a favor and work to insure high, unimpeachable internal quality standards. They will reflect to the consumers and it will show.
- Bonn-Miller et al. Labeling Accuracy of Cannabidiol Extracts Sold Online. JAMA 2017;318(17):1708–1709. DOI: 10.1001/jama.2017.
- Vandrey et al.Cannabinoid dose and label accuracy in edible medical cannabis products. JAMA 2015;313(24):2491-2493. DOI: 10.1001/jama.2015.6613.