Gas and liquid chromatography are used to quantify THC in cannabis and hemp products, and ongoing efforts aim to develop standard methods for the industry. Scientific technology editor (now creative services manager) Michelle Dotzert speaks with Ellen Parkin, quality assurance officer at Juniper Analytics, LLC, an ORELAP and ISO 17025 accredited cannabis testing laboratory in Bend, OR, about THC testing techniques and the associated challenges.
Q: What are the differences between cannabis and hemp?
A: Cannabis actually refers to the genus of the plant and encompasses both hemp and marijuana. The USDA classifies both hemp and marijuana as Cannabis sativa L. The difference lies in the delta-9-tetrahydrocannabinol (Δ9- THC) levels in each plant species. Hemp is defined as material that has less than 0.3 percent (by dry weight) Δ9-THC. Marijuana is defined as material that exceeds that 0.3 percent Δ9-THC threshold.
Δ9-THC as defined by the USDA includes Δ9-THC and tetrahydrocannabinolic acid (THCa) to indicate how much of the psychoactive component could be available to the consumer after decarboxylation.
Basically, the difference between hemp and marijuana comes down to an expression of THC or CBD (cannabidiol) dominance within the plant species. Hemp displays high CBD and low THC expression, while marijuana has low CBD and high THC expression.
Q: How does this information (THC content) affect the grower/ producer and the consumer?
A: For growers and producers, THC content can determine the price point at which they can sell to wholesalers and dispensaries. The difference between an 18.1 percent and a 21.3 percent flower could be the difference of $500 or more per pound.
From a consumption standpoint, the higher the THC content, the more Δ9-THC is available to interact within the body’s endocannabinoid system, specifically CB1 and CB2 receptors. This interaction will induce the psychoactive effects attributed to Δ9-THC. However, this is not to say that the higher THC strains you might find are “better.” There is a certain point where the body of a normal consumer (a person that does not consume on a daily basis) cannot tell the difference between the previously mentioned 18.1 percent and 21.3 percent strains. The strain itself can also affect how you experience the effects of the cannabis (e.g. calming and relaxing versus anxiety and paranoia).
The effects of THC can also change with how the product is consumed. Smoking flower or extract material will have an immediate effect, peaking within 30-60 minutes. Eating or drinking an infused product may take 20 minutes to 1.5 hours for initial effects and can last many hours. Some studies have even shown that the body can metabolize Δ9-THC into 11-hydroxy-Δ9-THC for different psychoactive effects.
Q: How is a representative sample obtained?
A: Many states allowing medical and recreational cannabis use have set standards for laboratories to obtain a representative sample of the batch of cannabis to be tested. This includes training guidelines for sampling staff, sampling plans for different types of cannabis products (e.g. flower, extracts, infused products), maximum batch weights or sizes, and a minimum required sample for the laboratory sampler to take. These guidelines require a percentage of the batch to be obtained as a representative sample. Here in Oregon, we are required to obtain a minimum 0.5 percent of the total batch weight for flower material to be tested. With a maximum batch size of 15 pounds, that equates to a maximum 34.2 gram sample of flower material to be sampled from throughout the batch and returned to the lab for testing.
Q: What techniques are used for THC testing? Is there a superior, or gold standard, technique?
A: Cannabinoid testing, sometimes referred to as potency testing, can be done on either an HPLC (high performance liquid chromatography) or GC (gas chromatography). Most laboratories have transitioned to HPLC analysis as this provides the laboratory with more reliable results for the acidic cannabinoids like THCa and CBDa.
Currently, there are not standard methods for this analysis or any analysis in the cannabis testing sphere. The lack of standardization stems from cannabis being a fairly new legal industry in the United States, coupled with laboratory competition and hesitancy to share knowledge. Our laboratory is looking to overcome these hurdles and work with groups like AOAC and ASTM to help build standard methods and implement them in the industry.
Q: Does total THC content include THCa? If so, how is this quantified?
A: Total THC includes Δ9-THC and THCa to indicate how much of the psychoactive component could be available to the consumer after decarboxylation. This is calculated using the following equation:
Total THC = [Δ9-THC] + [THCa x 0.877]
This equation assumes 100 percent decarboxylation of THCa into the active Δ9-THC cannabinoid. In its acid form, THCa has no psychoactive effect.
Q: Is it possible to determine the THC content of other cannabis products such as edibles, topicals, oils, tinctures, or teas? How does the sample matrix affect the analytical approach?
A: Yes, most cannabis laboratories across the country have developed methods to handle cannabinoid extraction from cannabis-infused matrices such as edibles, topicals, tinctures, etc. With each of these matrices, there may be different sample preparation steps to extract the cannabinoids from the infused matrix. After sample preparation, the analysis process is the same for identifying the final cannabinoid content of the products. For some products of very high concentrations (isolates) or very low concentrations (micro-dosed infused products), other analytical methods may be used to accurately quantify those cannabinoid levels.
Q: What are some challenges associated with THC testing and how might they be overcome?
A: As mentioned before, there are currently no standard testing methods for cannabinoid analysis. Therefore, when the cannabis laboratories first started operations in each state, they needed time to develop and validate preparation and analytical procedures prior to testing products. For those states that did not require extensive validation, many labs conducted development during production testing. As each laboratory was developing methods on their own and continue to have differences in their analytical methods, this can cause some differences in testing results from lab to lab, potentially resulting in differences in testing results.
A lot of challenges come from the matrix itself. Variability in tested values can be observed in a lot of infused products, and even flower material. Some infused products, like drinks, are difficult to infuse due to the hydrophobicity of the THC or CBD molecules. With other products such as gummies, homogenization and consistency are difficult to achieve within and across batches. Our laboratory does a lot of consulting with clients to help them dial in their process to provide consumers with consistent products.