By Dr. Daniela Vergara
Have you ever wondered how we figure out the levels of CBD, THC, and other cannabinoids in cannabis products? In this post, we’ll explain the science behind the methods used to measure cannabinoids, like chromatography and mass spectrometry, and how these techniques help analyze cannabis components.
Why Is Cannabinoid Testing Important?
Cannabinoid analysis is used for many reasons, including medical research and legal regulations. The main goal is to determine the potency and quality of cannabis products, but it also helps classify a sample as “hemp” or “marijuana” based on its THC content. This is useful for both consumers and professionals in the cannabis industry.
What Are Cannabinoids, and How Are They Made in the Plant?
Cannabinoids are chemical compounds found mainly in the Cannabis sativa plant. They are produced in tiny glandular structures called trichomes, which are most abundant in the flowers of female cannabis plants—what we commonly call buds.
Did you know that cannabinoids are first made in an acidic form? Their names end with an “A” (like THCA and CBDA). These acidic cannabinoids must be heated to become their well-known active forms, THC and CBD. This heating process, called decarboxylation, removes carbon dioxide (CO₂) and transforms the cannabinoids into their neutral, active state. You can read more about this in our previous post (link)
But how do we measure these cannabinoids in their acidic and neutral forms? Many different techniques are used, and we’ll explain some of the most common ones below.
What Is Chromatography?
One of the most common ways to measure cannabinoids is chromatography. This lab technique separates the different compounds in a cannabis sample so they can be identified and measured.
Think of chromatography like a race. The track is the stationary phase, which stays in place, while the runners represent the mobile phase, moving through the track. Cannabinoids behave like runners, moving at different speeds depending on their properties. Some stick to the track longer, while others move ahead quickly, allowing scientists to separate and identify them.
How Does Chromatography Work?
- Sample Preparation: First, a mixture containing the cannabis sample must be made. This could be flower, CBD oil, edibles, or any other cannabis product. The cannabinoids (also called analytes) are the compounds that will be separated and measured.
- Injection: The sample is pushed through a tube or column that contains a solid or semi-solid material (the stationary phase).
- Separation: Different compounds in the sample move at different speeds depending on their size, chemical properties, and how much they stick to the stationary phase.
- Detection: As the separated compounds leave the column, a detector measures how much of each compound is present. This is often done by seeing how much ultraviolet (UV) light they absorb.
- Data Analysis: The data is processed into a graph called a chromatogram, which helps scientists determine which cannabinoids are present and in what amounts.
Gas Chromatography (GC): Testing for Neutral Cannabinoids
How does gas chromatography (GC) work?
Gas chromatography (GC) uses gas to carry the sample through a thin tube (a capillary column). This method requires heating the sample to ensure it flows properly.
Because gas chromatography requires heat, it automatically decarboxylates acidic cannabinoids, turning them into their neutral forms. That means GC can only measure THC, CBD, and other neutral cannabinoids—not their acidic versions. This is one downside of using GC for cannabis testing.
High-Performance Liquid Chromatography (HPLC): Measuring Both Acidic and Neutral Cannabinoids
Unlike gas chromatography, high-performance liquid chromatography (HPLC) doesn’t use heat. Instead, it relies on a liquid solvent under high pressure to move the sample through a column. Since it doesn’t require heating, HPLC can measure cannabinoids in both their acidic (THCA, CBDA) and neutral (THC, CBD) forms.
Because it measures both acidic and neutral cannabinoids, HPLC is may be a better option to analyze cannabinoids. It provides complete and accurate results, making it very common in the industry.
Understanding Cannabinoid Test Results
After running a cannabinoid analysis, the result graph is called a chromatogram.
What does a chromatogram show?
The following figure shows the results of a cannabinoid analysis using High-Performance Liquid Chromatography (HPLC). This type of graph is called a chromatogram, and it helps scientists separate and measure different compounds in a sample.
- X-Axis (horizontal): Represents time (in minutes). Each compound, or cannabinoid, takes a different amount of time to pass through the system, which helps identify them.
- Y-Axis (vertical): Represents signal intensity, measured in milli-Absorbance Units (mAU). This tells us how much of a cannabinoid is present. The higher the peak, the more of that cannabinoid is in the sample.
Each cannabinoid has a unique retention time, meaning it appears at a specific point on the X-axis. These times are compared to known standards to identify each compound. The Y-axis measures how much light each cannabinoid absorbs, which helps determine its quantity.
By looking at the chromatogram, we can see which cannabinoids are present in the sample and how much of each is there. This method is essential for testing cannabis potency and quality.
How do we know which cannabinoids are in a sample?
Each cannabinoid has a unique retention time, meaning it appears on the chromatogram at a specific point. By comparing the peaks on the graph to known standards, scientists can identify and quantify the cannabinoids in the sample.
Cannabinoid testing is essential for ensuring the quality, potency, and legal classification of cannabis products. Chromatography, especially HPLC, is the best method for analyzing both acidic and neutral cannabinoids, giving a full picture of a cannabis sample’s composition.
Next time you see a label showing the THC or CBD content of a product, you’ll know the science behind it!
