Cannabis Quality Testing: the Why and the How

While the term “cannabis testing” might conjure up images of people being drug tested, now that cannabis is a cash crop it has taken on a whole new meaning. Cannabis testing nowadays is more likely to refer to the practice of quality control for cannabis companies.

In a recent webinar, the National Cannabis Industry Association (NCIA) outlined the various ways commercial cannabis is tested for quality purposes and the problems with how testing is done.

Board members of the NCIA’s advisory committee conducted the webinar:

• Alena Rodriguez, Managing Director at Rm3 Labs; 
• Garrett Cropsey, Project Manager at Canna Advisors; and 
• Tiffany Coleman, Director of Quality at Copperstate Farms.

Why test?

The top reason for testing cannabis that will be sold commercially is because consumers have the right to know what is in the products they are using. These consumers can include medical patients, recreational users and veterinary patients. In addition to consumers, people involved in the processing of the cannabis also deserve to know what they are handling. 

Cannabis is tested for five different elements:

1. Safety
2. Identity
3. Strength 
4. Purity
5. Quality

The first four elements all support the fifth, quality. 

Safety

Testing for safety simply means making sure the product is safe to handle and consume. In the case of cannabis, quality testing is regulated by municipal and state legislatures. 

Part of testing for safety includes performing composition testing, to see what is in the cannabis flower itself. 

Identity

Identity means that what the label says is in the package is actually in the package. In terms of cannabis flowers, that means knowing that it is a contaminant-free cannabis flower that is in the package. In the case of edibles, it means identifying everything that is contained in the edibles. 

Strength

Strength is about the potency of the product, which is important in the cannabis industry. Testing for strength includes potency analysis to make sure what goes on the label is accurate in terms of strength. If the strength isn’t accurate, the identity of the product cannot be accurate.

Part of establishing the strength of the cannabis is a cannabinoid analysis that looks at the potency of THC and THCA, which are the active and inactive forms of cannabinoids, respectively, in the flower.

The formula for determining potency is: Total [cannabinoid] = [cannabinoid] + ([cannabinoid-A] x 0.877). 

In that formula, 0.877 is used to account for the molecular weight difference of the two different types of cannabinoid, THC and THCA. The acidic form of the cannabinoid, THCA, has additional molecules that give it a slightly higher molecular weight.

There are several ways to test for potency and that includes doing a terpenoids analysis. Terpenes are organic compounds that give cannabis its aroma and flavor and also helps to enhance the effects of the THC. Without testing for terpenes and providing consumers with identification of the cannabis they are buying, consumers just go by the smell of the products if they want to judge the quality of it.

Testing can provide identification for the flavor and smell via gas chromatography–mass spectrometry (GC/MS) or liquid chromatography–mass spectrometry/mass spectrometry  (LC-MS/MS) testing.

Moisture content & water activity

Moisture content determines how much water is in the product while water activity determines how microorganisms are reacting with the water that is in the product.

Cannabis producers should test for both water content and water activity to make sure their water content is sufficient while reducing microbial contamination growth. Performing these two tests also makes sure potency tests are accurate, since the more water content in a plant, the less potent it appears because the weight is greater.

Testing for moisture content and water activity tells the cannabis producers how long their product will stay good for without getting moldy or degrading. There is a sweet spot for water content where producers are able to maintain plant quality while also protecting against microbial contamination. 

Types of moisture tests include a loss on drying test; a capacitance tester, which is a handheld device; a Karl Fischer titration test in the lab or a specific water analyzer in the lab to perform the screening.

Purity

Purity means the product is free from contamination from either chemical or microbial elements. 

These can include things like heavy metals and pesticides or more common everyday contaminants like hair, dust from things like broken ceiling tiles in the processing area or rust from degraded pipes. 

Chemical contaminant testing determines if the product contains any third-party chemicals that it should not, such as:

• residual solvents
• pesticides
• heavy metals

Yeast and mold testing is done to make sure the product is free of bacteria and mycotoxins

Dangers of microbial contaminants

Testing for molds, yeasts, bacteria and toxins left over from microorganisms is crucial because objectionable organisms like mold can actually cause harm to people.

Aspergillosis, for example, is a fungal infection that can occur in people with compromised immune systems when they inhale a certain type of mold into their lungs. There have been case studies of it originating from contaminated cannabis products and there has been at least one healthy person who has been infected with cryptococcal meningitis, a serious infection affecting the brain, from yeast inhaled on contaminated cannabis. 

Bacteria that can contaminate cannabis includes e coli and salmonella among others. Mycotoxins, which are secondary metabolites naturally produced by molds, are also of concern. Mycotoxins themselves are not alive, but they are the harmful poisons left over from molds.

Dangers of chemical contaminants

Some contaminants are leftover chemicals from processing the cannabis for various products. For example, for some kinds of edible and smokable products, the THC is extracted using solvents. If there are any residuals from these solvents, they can make people using them or even employees processing them sick. 

There are well-established tests for screening for residual solvents that go back decades using GC/MS screening. If these tests show that residual solvents are at acceptable levels, producers know their quality control processes are working. If solvent levels are too high, that indicates a problem with processing the extracts.

Pesticides used during the growing process are also a concern for producers. Each state has its own list of pesticides that cannot be present in cannabis, and the federal government has a list of pesticides that cannot be present in food, which can be used for cannabis edibles. It is imperative to know if there are any pesticides, herbicides or fungicides on cannabis flowers, especially if a producer is making edibles or concentrates from it. As the cannabis is concentrated, so are any contaminants that might be on it. 

Testing for pesticide chemicals can be done via GC-MS/MS and LC-MS/MS. If this type of testing is not performed, it can lead to significant recalls of products, which has happened a number of times already in the United States. A lack of this type of testing can also lead to significant health risks for consumers and for workers who have to handle the product. 

Heavy metals must also be tested for because they can accumulate in the human body over time and lead to complications like Alzheimer’s and Parkinson’s diseases. Cannabis is known as a “hyperaccumulator” of heavy metals because if it is grown in soil or with water that has a lot of heavy metals, it will collect these in its roots and stalks. This means heavy metals might be present in larger quantities than normal in this type of situation because of the type of plant it is. 

As with solvents, there are well-established processes for testing cannabis for heavy metals that go back decades that include Inductively Coupled Plasma Mass Spectroscopy (ICP-MS), which is the international standard of testing for elements like lead, arsenic, cadmium and mercury.

Interpreting Test Results

When testing cannabis, there are quantitative and qualitative measurements that can be taken. 

Quantitative testing

As the name implies, quantitative testing provides the quantity of what you are testing, so it actually measures the amount of the substance you are testing for within the substance being tested. 

For example, potency tests for cannabis give you an actual number for the presence of THC. 

Qualitative testing

Qualitative testing, on the other hand, does not tell you how much of what you are testing is present in the substance being tested. It merely tells you if it is present or not. They are usually used for descriptive purposes.

For example, testing for a certain bacteria might tell you if it is detected, but not give you any measurement of it. 

How the two tests work together.

Quantitative measurements are often used in qualitative reports to describe the presence of an analyte (something being tested for). 

For example:

5 - 10 units (quantitative) of an analyte = medium density (qualitative). Therefore, a measurement of 7 would be described as medium density. The quantitative measurement of 7 is being used to describe the qualitative density of the analyte.

Acceptable levels of contaminants 

Each state has its own acceptable levels of contaminants like chemicals and microbial contaminants. Some of these can vary greatly between states. For example, in California, the acceptable limit for the pesticide Imidacloprid is 5,000 parts per billion (ppb) vs 20 ppb in Colorado. 

Similarly, testing for microbial contaminants varies across states, too. For example, in California, companies are required to test for the fungal species aspergillus, but in Colorado, Oregon and Washington companies are not obligated to test for it. 

The differing regulations makes producing and testing cannabis difficult in the US. It’s up to each individual laboratory to ensure its equipment is capable of testing for the necessary elements and detecting those elements at the levels mandated in the state the products are being sold in. 

These vastly different levels and requirements for testing illustrate the point that the acceptable limits posted by states have more to do with regulation than actual safety. For example, cannabis might pass testing for microbial contaminants with a low colony-forming unit (CFU). But, under the right conditions -- like if the moisture content and the water activity level are too high -- that same batch of cannabis might fail the microbial contaminant testing later after its been sitting on the shelf for a month.

Conversely, a contaminant being over a certain limit does not mean guaranteed harm for someone who uses it. For example, if a state’s acceptable limit for a contaminant is zero, and if the product has a contaminant level of less than 5 ppb, that product wouldn’t be harmful to someone if they used it even though it’s technically over the accepted limit. 

Lab result variability 

Different laboratories can have varying results when testing the same product and this can be for a number of reasons. 

There is a lack of standard sampling protocol in the cannabis testing industry, so labs have no set of guidelines to follow when it comes to testing. Because cannabis is heterogeneous in nature, two samples taken from the same plant might have different cannabinoid concentrations depending on what part of the plant they were taken from. 

Contamination is also not evenly distributed throughout a harvest or production batch of cannabis. So, a flower that was chosen to be tested at one lab might not have as much contamination as another flower chosen from the same batch and sent to another lab. 

There is also a lack of standardized testing methods. Different labs will have different ways of storing the cannabis, preparing it for testing and extracting the analytes from the samples. For example, some labs dry the cannabis flowers prior to potency analysis while others do not. This means the flowers may have different moisture content during potency testing at various labs, which affects the potency results. 

While the same instrumentation is generally used for testing throughout the industry, different analytical parameters may be applied across laboratories. 

Lastly, labs may differ in their quantification of doubt, meaning the amount (positive or negative) that results may vary. (The +/- of results, in other words.) This means that even if the same testing methods are being used, inter-lab results will be similar, but not the same because of this differing uncertainty with results. 

Value of Collecting Testing Data

Establishing testing data history is valuable for a business because it provides insights into trends about cultivation and processing of the product that can be helpful for the future. The data can be used to quantify the effects of process changes. For example, it can be used to determine if changing the nutrients fed to plants enhances potency. 

It can also be used to pinpoint problems in processes and fix them. If, for example, the moisture content increased to a problematic point shortly after a new harvest manager is hired, that may point to an issue with the new manager’s drying and curing methods.

Cannabis testing supports quality of products by ensuring safety, identity, strength and purity. Although the need for safe cannabis products is obvious, the wildly differing testing requirements across states along with a lack of standardized practices in laboratories makes cannabis quality testing inconsistent throughout the country.