All cannabis products must undergo testing to identify the compounds within, possible aflatoxins, microbiological contamination, the total aerobic plate count, amount of yeast and molds, the total coliforms, ensure no salmonella, E. coli or heavy metals including inorganic arsenic, cadmium, lead, methyl mercury and residual solvents are found in the product, as well as a pesticide screening and a uniformity test. All of these tests are performed on the dry plant material used in cannabis products, a second time before dilution if the plant material is used in an oil, and a third time during the final product testing.
There are two primary methods of testing the phytocannabinoid content of cannabis, gas chromatography (GC) or liquid chromatography (LC). GC is less popular due to it changing the phytocannabinoid composition of samples unevenly each time. The machine performs the analytical test with heat in an oven, which has been found to alter up to 70% of the phytocannabinoid acids and creating significant discrepancies in the results. By the time the sample is actually scanned, it only picks up decarboxylated phytocannabinoids. GC is relatively worthless for testing edibles, as you need to be able to tell the difference between inactive THCa and psychotropic THC. LC, on the other hand, is a safer alternative that doesn’t use heat to determine the molecular composition of samples. This is the more popular method due to the lab results being more accurate and showing the exact amounts of all phytocannabinoids.
When the lab results return, a few conversions need to happen before they’re truly accurate. When phytocannabinoid acids are decarboxylated, they lose about 12% of their mass, so the acids do not convert to phytocannabinoids in a 1:1 ratio. A strain’s results of 15% THCa and 2% THC does not mean 17% THC when smoked or baked. Using the molecular weight of these compounds, divided by the weight of the heavier phytocannabinoid acid molecules, we learn the conversion ratio is 0.877:1 phytocannabinoid:acid. This means a single gram of THCa would only contain 877 mg of THC when fully decarboxylated; likewise for CBD. This would mean our sample would actually only contain 15.155% THC. Even less THC will be found in baked goods, however, with a ratio of 0.333:1 THC:THCa.
This may still not be entirely accurate, however. Some large-scale and dominantly corporate cultivation facilities ship their harvest off for testing to multiple laboratories, and they’ll publicize the results that give the highest numbers. The laboratories that gave lower numbers will lose out on business, so some lab technicians have been instructed to cherry pick buds with the most trichomes and treat that as an average sample. It’s by no means a standard in the industry, but a growing issue to be sure. According to Andy Hospodor, a medical cannabis and data forensics expert in federal court, he estimates that some Certificates of Analyses (COAs) in 2019 have a true phytocannabinoid content in homogenized biomass of around half of what’s being commonly reported. This means a 32% THC bud, even with the proper paperwork, might actually be as low as 15% THC for most of the bud.
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