Comprehending Your Cannabis Test Results
No matter the reason you tested your cannabis plants, the lab results are useless if you don’t know how to read the report. Jodi McDonald gives us the lowdown on cannabinoid potency reports and how to get the most out of them.
People who send cannabis products to the lab for testing typically fall into one of three categories. The first type of tester wants clinical confirmation of the cannabinoids their expertise tells them should be in the product.
The second type of tester is usually someone who likes to experiment with the growing conditions and wants to see how their changes affected the potency of the product.
The final group of testers are worried about dosage safety. They may have a product of questionable provenance or simply do not have enough information on their cannabis to make decisions about appropriate dosage.
While the lab results will provide answers to all the above inquiries, what most people don’t know is that there are hidden gems of information in the graphs and charts of a test report that give added insight to growers about their product.
What's in a cannabis product test?
Let’s take a closer look at a sample cannabinoid potency report (Fig. 1). The first thing you see at the top of the report is the identification information about the testing method. Immediately below that, you will notice a picture (Fig. 2). This is a chromatogram from a high-performance liquid chromatography (HPLC) instrument and it is essentially a fingerprint of the product. This graph is particularly useful for ongoing testing; one can simply compare the graphs to see if the peaks and valleys change—and thus, the product itself changes—over time.
Below the HPLC chromatograph are two charts that highlight the cannabinoid potencies of your product. The first chart identifies cannabinoid concentrations (Fig. 3). As you can see, the delta-9-tetrahydrocannabinol (THC) level is 24.64 per cent (the product sample analyzed in this example is a cannabinoid extract, so the concentrations are much higher than what would occur in dried flowers).
As you can see in this example, the levels of tetrahydrocannabinolic acid (THCA)—the carboxylated form of THC—is at 56.26 percent. This result tells us that the tested extract has not been decarboxylated very efficiently; ideally, the THC level should be higher than that of the THCA. In fact, if any carboxylated cannabinoid concentration is higher than that of its corresponding the decarboxylated form, we know that the decarboxylation process is not as efficient as it could be.
In the final section of the report, there is a chart to show the potency totals of each cannabinoid family (Fig. 4). These values represent typical concentrations if an efficient decarboxylation process is used. While the carboxylated and decarboxylated cannabinoids are grouped together for this section, the family totals are not calculated with straightforward addition.
Labs first use a conversion factor, which is specific to each cannabinoid to account for the weight of the carboxyl group, to calculate a new total percentage for the acid form. These conversion factors are listed in small print below the totals chart (Fig. 5). In this example, a conversion factor of 0.877 is used for the THC family group.
Calculating weed potency
Here’s how one would use that factor in calculating the total potency for that cannabinoid family:
24.64 per cent
56.26 per cent X 0.877 = 49.34 per cent
THC (24.64) + THC-A (49.34) = 73.98 per cent
Near the bottom of the report are two key numbers (Fig. 4). One is the activated total, and the other is the THC to CDB ratio. The activated total, which is calculated with a straightforward 1+2+3 = 6 formula, represents the sum of all the decarboxylated cannabinoids that were measured. The THC to CBD ratio is included here as a quick reference for individuals who are targeting a specific ratio for its therapeutic benefits.
While a single test can provide anyone with a wealth of information, testing over time can be particularly useful to cannabis producers. Each change made in the growroom or to the post-harvest process can have an impact on cannabinoid potency, and ongoing tests can provide producers with a richer understanding of how their processes affect their product. Growers quickly begin to recognize the unique fingerprint of their products, and thus know at a glance when things are working perfectly or when production requires some attention.