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Hemp Testing for THC and Other Cannabinoids: A Closer Look at How Hemp Lab Testing Works

ByTrichome Team

November 25, 2020

Reading Time: 5 minutes

Pre-harvest testing for hemp THC potency is an essential (and mandatory) aspect of the U.S. hemp program as outlined in the 2018 Farm Bill. Beyond the harvest, cannabinoid testing for research purposes, as well as product development, is also vitally important for this burgeoning industry. 

Per current federal regulations, the goal of pre-harvest testing is to verify that a hemp crop has less than 0.3% THC on a dry-weight basis. But tetrahydrocannabinol (THC) is just one of many notable cannabinoids found in the species Cannabis Sativa L

There are more than 100 known cannabinoids, such as cannabidiol (CBD), cannabigerol (CBG) and tetrahydrocannabivarin (THCV) to name a few, and they all have unique properties and pharmacological effects. Knowing your product’s full cannabinoid profile can help you better understand its best applications and uses.

We’ll walk through how testing labs measure cannabinoid content and document the test results in Certificates of Analysis (COAs). 

Not Just THC: Cannabinoids in Hemp 

THC, or more accurately, delta-9 tetrahydrocannabinol, may be the most well-known of all cannabinoids. But THC content is only a small part of the picture. As science surrounding cannabis and its health benefits continues to develop, other cannabinoids are starting to be studied in depth for their distinct properties and effects. 

For example, THCA is non-psychoactive and is the most abundant cannabinoid found in raw cannabis. Studies have shown it to be neuroprotective, antispasmodic and anti-inflammatory. CBD has a wide variety of applications. It has been clinically proven to decrease the frequency of seizures in children, and an increasing number of studies indicate it could help with management of anxiety, insomnia and chronic pain. 

At Trichome Analytical, we test for the presence and potency of 15 cannabinoids in plant material, extracts and infused products. These cannabinoids include CBC, CBCA, CBD, CBDA, CBDV, CBDVA, CBG, CBGA, CBL, CBN, delta-8 THC, delta-9 THC, THCA, THCV and THCVA. 

Knowing the cannabinoid composition of your hemp product is vital to understanding its potential health benefits and usage recommendations. 

How Does a Lab Test a Hemp Sample for Cannabinoids? 

Lab testing is a straightforward process. First, the cultivator or processor sends the lab a sample of plant material, extract or infused product, making sure to adhere to regulations concerning compliant mailing and chains of custody

Trichome Analytical, headquartered in Mount Laurel, New Jersey, serves hemp producers throughout the Northeast, from Pennsylvania to New York, Maryland and beyond. We can receive samples submitted by mail or dropped off during our business hours.

The amount of material for testing varies depending on what kind of sample it is—from 1g for concentrates, up to 10 grams or more for fresh cut plant material.

Once the sample arrives, it is registered into our LIMS (laboratory information management system) and assigned unique laboratory IDs. The information recorded indicates to the technicians what type of analyses the sample is to be processed for. From the moment the sample arrives at the laboratory, everything that happens to the sample is recorded and traceable—from the solvents used to the technicians touching the sample.

After any required drying, the sample then proceeds to preparation for cannabinoid analysis. This involves homogenizing, weighing, extracting and diluting. Different products require additional techniques such as sonication and winterization. Further dilution is used for high cannabinoid concentrates and extracts. The purpose of these techniques are to remove interfering compounds (fats, lipids, etc.) and to extract all of the cannabinoids from the subsample into a solution. This process results in diluted liquid extracts of the product that can be injected into our UHPLC-PDA and measured.

Hemp flower post-homogenization
Hemp flower post-extraction, prior to dilution

At Trichome Analytical, we test for cannabinoid potency using a process called ultra high performance liquid chromatography (UHPLC) with UV-PDA detection. Liquid chromatography is used in the process to measure cannabinoid content as it does not decarboxylate the acidic cannabinoids like gas chromatography would.

The prepared sample is injected into the HPLC column mixed with a mobile phase (liquid carrier solvent). The column is packed with a stationary phase. As the mobile phase, mixed with the sample, passes through the stationary phase, some compounds are retained on the column longer than others. This causes the compounds to flow out of the column in a specific order.

Interior of a HPLC system – HPLC column is on the right

After the compounds are separated by the column, each is exposed to UV light at an array of wavelengths. Each compound (i.e., different cannabinoids) absorbs wavelengths of UV light differently and the amount of compound present affects how much light is absorbed. By measuring the absorbance of UV light, PDA detection allows us to quantify how much of a certain compound is present in the solution. Now that we have measured the concentration of compounds in the prepared solution we can back-calculate the amount in the original sample by adjusting for extraction volume, dilution, and sub-sample mass.

So how long does this process take? Beginning to end, with just one dried flower sample and no workflows to worry about: About 3 hours. However, we have many quality control samples that we run alongside yours to make sure our instruments (and people) are performing correctly. You can expect rush results in 1-2* business days, or a regular turnaround in 5-7* business days.

Certificates of Analysis, Explained

Certificates of Analysis (COAs) document precise measurements of the contents of a given hemp sample. 

For example, a typical cannabinoid potency analysis for plant material from our lab would include a measurement of the sample’s cannabinoid levels expressed as percentages—that is, what percentage of each cannabinoid is present in the sample by dry weight. Depending on the type of sample provided (plant material, extract or infused product), we report in weight percent, mg/g, and / or mg/mL. 

If you are a hemp cultivator looking for total THC measurement compliance, your result will be clearly marked to show whether it falls above or below the 0.3% potency limit. While the U.S. Department of Agriculture mandates pre-harvest compliance testing, you are able to request tests on your hemp crop at any time to gain an understanding of your plant’s cannabinoid content, terpene profile or other testing aspects, such as pesticide residue or foreign-material contamination. 

Terpene profiling is included as part of our standard profile panel to give cultivators and processors a better idea of the potential applications, flavor aspects and potential entourage effects lent by the terpenes. This result is expressed in a bar graph with terpene content expressed as a percentage by weight. 

Results from other tests ordered, like moisture content or heavy metal screening, will also be clearly displayed on the COA. 

Lab testing, whether for THC content, cannabinoid and terpene profiles, heavy metal presence, pesticide residue or microbial contamination is the best way to ensure your crop or hemp product is safe and compliant. 

Want to learn more about how testing works? Contact our team today. 

*drying, if needed, adds 1-3 days to the turnaround