How Cannabis Samples are Tested for Potency

by | learn

Trevor originally wrote this article for Growers Network (a private community for commercial cannabis growers).

With their permission, we’re posting the full article below.

Cannabinoid potency tests are performed using High Performance Liquid Chromatography (HPLC) machines. Yay, article’s over!

Just kidding. What does an HPLC machine actually do?

Let’s start with the “C” in HPLC, which stands for chromatography. Chromatography is an analytical technique used to separate compounds based on their physical and chemical properties. Imagine you have a bunch of ping-pong balls with different weights. These ping-pong balls are sitting in a bucket that has an air pump attached to the bottom. As you turn on the air pump, the lightest ping-pong balls will start to fly out of the bucket. You can collect and count all the ping pong balls that fly out of the bucket, turn up the air pressure, and count the next group of ping-pong balls that fly out. If you continue turning up the air pressure, even the heaviest ping pong balls will fly out of the bucket.

Chromatography essentially works the same way:

  1. The ping pong balls represent different cannabinoids and their respective weights. Different cannabinoids have different chemical and physical properties.
  2. The bucket represents an analytical column. Solvents travel up the analytical column and pull the cannabinoids with them.
  3. The air pressure represents the strength of the organic solvent. Stronger solvents will pull up cannabinoids at greater speeds.
  4. Counting the number of ping-pong balls represents the signal strength measured by a detector.

Diagram of an HPLC machine. On the right side, you see the separatory column and detector. On the left are the solvents.

Samples received here at AgriScience Labs are carefully weighed and extracted by our trained analysts. The extracted solutions are then injected into an HPLC instrument with a stream of organic solvent. The sample is pushed through the analytical column, separating the different cannabinoids based on their physical properties. The strength of the organic solvent is gradually increased and the separated cannabinoids are removed from the column at different times. The cannabinoid compounds are then sent to a detector which produces a signal strength that correlates with the amount of each cannabinoid. This data is then processed by our scientists to determine how much of each cannabinoid is present in your sample.

Of course, this is a simplification of the actual process for determining the amount of each cannabinoid, but hopefully you now have a general idea of how your samples are analyzed for potency.