As anyone with even rudimentary experience using cannabis can tell you, potency can vary a lot. Sometimes that can be half the fun, learning just what effects a new strain will have and how strongly you will experience them.
But if you are a medical marijuana patient, cannabinoid potency can be a very important factor in your therapy. Cannabis from a MMJ dispensary, if you have access to one, will often be laboratory tested. The results from these analyses can help guide a patient in selecting a strain with the right cannabinoid potency and ratio to give the desired effect.
If you are growing your own herb, or getting it from a source that has not tested it, there are options available for you to determine its potency. If you live in a state that has legal weed, there may be a commercial lab near you that performs potency, contamination and other tests on samples you provide to them. But lab tests can be costly, running about $60 or more for each potency analysis.
Options to do your own potency testing are available online, but do they work?
That is what I wanted to find out, so with the help of San Diego cannabis testing facility PharmLabs, I put the tests to the test to run my experiment, I performed the different tests as directed. I used samples of cannabis flower from batches tested for potency by PharmLabs with their gas chromatograph lab equipment.
My goal was to compare the results I obtained from the home testing options for THC and CBD potency, with the lab results provided by PharmLabs, to see if they were consistent. The manufacturer suggest running multiple tests on several samples from a batch and determining averages for the most precise results.
The first products I tried were Test 4 Detection Kits by CB Scientific. I tried individual tests for THC or CBD, there is a combination test available as well. These are very simple kits that only require a small pinch of herb, added to a container with a test fluid. After a good shake and a few minutes wait, the color of the sample is compared to the included reference chart. A color match determines a range of potency, rather than a precise number.
All the results I received from the CB Scientific products were some what consistent with the PharmLabs results. The potency ranges on the reference card top out at only 20 percent THC and only 2.5 percent CBD, so if your sample is stronger, you will not know by how much actual THC or CBD is in each sample, so the test has some limits.
If you are looking for results with greater precision, or an even lower cost per test, the other products I tried may better fit your needs.
These types of kits use a process called thin layer chromatography (TLC). One of the products I tried was CTK Test Kit #1 from TLC Lab Supply. Although a more involved and technical process, more precise results can be obtained with the thin layer chromatography options. Although I was only looking at THC and CBD, about a half-dozen different cannabinoids will render on the plate, CBG, CBN and acids were also able to be tested.
To perform these tests, a 0.1 g sample of flower is mixed with a test fluid. Very small samples of the mixture are precisely measured and applied with a pipette or capillary tube to a specially coated glass plate. The plate is then placed in a jar, standing in additional test fluid. The fluid then wicks up the plate, carrying the cannabinoids with it. The individual properties of the cannabinoids cause them to be left in line, in a particular color and specific order, up the plate. Once the plate is dry, it is sprayed with a dye to reveal the colored spots. The size of the spots is compared to a template, which determines potency results in increments of one percentage point.
You might feel like you are on CSI with this process, as Mr. Green from TLC Lab Supply noted, his company offers classes in three states ( with more to come) to learn the more detailed types of testing of different products in cannabis from a qualified professional.
Many variables, such as dryness of the sample and precise measurements, must be accounted for. I was able to perform tests that matched, within one percentage point, the numbers obtained by PharmLabs.
The TLC Lab Supply CTK Test Kit #1 is available for $160 and will test up to 25 samples. with free shipping in the USA.
I only tested flower for my experiment, but the products I tried can also be used for concentrates and many other cannabis products.