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Avoiding Pitfalls When Testing Cannabis Products

Avoiding Pitfalls When Testing Cannabis Products

Testing Cannabis Products

What Producers Must Know

There is no doubt that today’s cannabis producers are having to deal with the risk of doing business in a highly ambiguous and volatile regulatory environment. No need to look any further than the Food and Drug Administration’s (FDA) most recent ruling on cannabidiol as a New Dietary Ingredient FDA Rejects Full-spectrum CBD as a Dietary Supplement | Forbes or into the potential implications of testing fraud America’s Pot Labs Have A THC Problem | FiveThirtyEight to give producers pause. Much of this ambiguity has to do with the fact that hemp derived products have been adopted federally whereas medicinal and recreational marijuana products have only started to become legal at the state level, leading to a variety of sometimes conflicting requirements. With all this uncertainty in the market, what are reputable cannabis and hemp producers to do?  This article will cover the differences between CBD and THC, outline proper testing for identifying and testing those compounds and finally, give cannabis producers a guide to asking the right questions when choosing a laboratory testing partner.

CBD vs THC – What’s the difference?

Hemp and marijuana are both types of Cannabis (Cannabis sativa); however, they are differentiated primarily by chemical composition and characteristics. Hemp plants are generally tall and durable, while marijuana plants are typically shorter with many flowers. Both cannabis plants contain more than 80 biologically active compounds called cannabinoids, of which, D-9-tetrahydrocannibinol (THC) and cannabidiol (CBD) are most well-known. These compounds exert their effects by interacting with specific cannabinoid receptors present on the surface of cells of the central nervous system and are categorized based on their degree of psycho-activity. For example, THC is known to be psychoactive (makes a person “high”) while CBD is known to be analgesic.

Hemp plants contain little to no THC but have an abundance of CBD and other similar structured cannabinoid components. Hemp plants and their products are regulated by the USDA and by law must contain less than 0.3% of THC by weight. Industrial cultivation of hemp was banned by the Controlled Substances Act of 1970 which classified all cannabis (hemp and marijuana) as Schedule I drugs. However, the 2014 Farm Bill, clarified the legal difference between hemp and marijuana, which paved the way for the 2018 Farm Bill that allowed for growth of hemp plants by farmers. This in turn has allowed for regulation of hemp and hemp derived products.

In contrast with hemp, marijuana can contain high concentrations of THC (upwards of nearly 40%) while also containing an abundancy of CBD components. In this light, stricter standards of testing of marijuana products are mandated by states where this form of cannabis has been legalized for medicinal and recreational purposes. Recent legalization of marijuana usage in many of the states, over and above the previous legalization of hemp growth, has resulted in a boom in growers, manufacturers, wholesale and retail distributors and consumers of cannabis products.

Why is cannabis testing an important aspect of its regulation? To address this question, it is instructive to look at the biological effect(s) of the active components in the two classes of plants in the Cannabis sativa family (hemp and marijuana). These active components, known generally as cannabinoids [including, but not restricted to, D-9-tetrahydrocannabinol (THC), cannabidiol (CBD), THCA, CBDA, CBG, CBN] act in the brain by way of the endocannabinoid (EC) system which includes cannabinoid receptors to which endogenous cannabinoids bind and modulate neurotransmitter mediated communications. This system is a unique communication system in the brain and body that affects many important functions, including how a person feels, moves, and reacts (hunger, pain, memory and even mood). A compound such as THC competes with such binding and interferes with normal physiological function. Thus, presence of THC at levels much higher (as can potentially happen in unregulated cannabis products) than those of the endogenous ligands can dominate normal neurophysiological functions and lead to unintended effects. In this light, of the need for regulation of cannabis products can be seen.

How to Properly Test Cannabis Products

What follows is a summary description of cannabis product tests as well as an outline of some of the equipment required for this testing.  It should be noted that not all tests are necessary for all products as some tests are product specific.  Table 1 lists the tests and the products to which they are applicable. 

Table 1:  List of currently mandated testing of cannabis products along with their applicability [1].

Test Conducted ForTest DescriptionProducts Applicable To The Test
Cannabinoids (Potency testing)Measure concentrations of THC, THCA, CBD, CBDA, CBG and CBN.  Important for correct classification of hemp and correct dosing of medicinal marijuana patients.All
Foreign materialDetermines presence of foreign material (hair, insects, feces, packaging contaminants and manufacturing waste)All
Heavy metalsConfirms limited presence of heavy metals (arsenic, mercury, lead, cadmium and chromium)All
PesticidesConfirm absences and limited presence of pesticide residues (details vary by state)All
MycotoxinsScreens for Aflatoxin B1, B2, G1 and G2, and Ochratoxin A. Potentially harmful for immune-compromised consumers.All
Microbial impuritiesScreens for Shiga toxin —E. coli, Salmonella spp. and pathogenic Aspergillus speciesAll
Residual solvents and processing chemicalsConfirm absence of class I residual solvent and limited presence of class II and III solvents and processing chemical residuesManufactured cannabis products or pre-rolled cannabis
Moisture content and water activityMeasures moisture content and water activity according to type of productFlowers, processed solid and semi-solid products
TerpenoidsCheck for conformity to the labeled content of terpenoidsAll labeled products

Potency Testing: The most common cannabis testing is the analysis of cannabinoid profiles, also known as potency. This test is applicable to both hemp and marijuana derived products. Cannabis plants naturally produce cannabinoids that determine the overall effect and strength of the cultivar. Most states only require testing and reporting for the dry weight percentages of Δ9-THC, and cannabidiol (CBD). Therapeutic CBD is desirable for medicinal effect, but the psychoactive THC may or may not be desired. This THC to CBD ratio information is of primary importance to medical personnel prescribing cannabis for medicinal purposes. A major cannabinoid in the cannabis plant material is THC Acid (THCA) which is thermally labile and converts to THC by decarboxylation during heating which, for example, can occur in a hot gas chromatography (GC) injector port. For this reason, THCA is not detected by GC but is detected by high performance liquid chromatography (HPLC). Similarly, CBD acid is also thermally labile and is difficult to be detected by GC.

Heavy Metal Testing: Different types of metals can be found in soils and fertilizers, and as cannabis plants grow, they tend to draw in these metals from the soil. Heavy metals (most commonly lead, cadmium, arsenic, chromium and mercury) are a group of metals considered to be toxic and hazardous and are required to be tested to confirm their levels are under certain toxic thresholds. Without specific methods of regulation from the individual states, FDA guidelines for heavy metals in food products need to be followed. Heavy metal testing is typically performed by inductively coupled plasma mass spectrometry (ICP-MS). This technique uses the different masses of each element to determine which elements are present within a sample and at what concentrations.

Residual Solvent Testing: Extracted concentrates of cannabis are formulated into hash oil, wax, butter, liquids, edibles and pills are popular amongst users who do not wish to smoke cannabis products. Extraction takes place with several types of solvents such as butane, propane, ethanol, isopropanol, acetone and others. After post-extraction processes like winterization, vacuum and heat, residual solvents that remain behind can be ingested or inhaled by users in appreciable quantities. For safety purposes, solvents must be removed from the final product before consumption. Cannabis residual solvent analysis ensures that product safety and quality standards are met. Residual solvents are divided into three classes I, II and III.  Of these, class I solvents should be avoided as they are known and suspected carcinogens and environmental hazards. Class II solvents are recommended to be within regulated limits as they could be potential teratogens, or reversible neurotoxins. Hexane is the only Class 2 solvent routinely found in cannabis extraction solvents. It has been linked to respiratory irritation, dermatitis, liver and kidney failure, and Parkinson’s Disease and as such hexane levels should be as low as possible to avoid unwanted side effects. Class III solvents are safer to use and may be subjected to higher limits of presence than class II solvents.

Residual solvent testing identifies the presence of these potentially harmful compounds, along with impurities and other trace residues. It is a crucial way to assess the efficiency of manufacturing processes and ensure that the finished products are safe for consumption. Residual solvents are measured by gas chromatography with headspace and flame ionization detection (GCHS). Tolerances for the class I solvents (e.g. 1,2-dichloroethane, benzene, methylene chloride, trichloroethylene) are much more stringent than for Category II solvents (e.g. acetone, butane, heptane).

Pesticide Testing: There are many pesticides that areused in commercial cannabis operations to kill the pests that thrive on the plants and in greenhouses. These chemicals are toxic to humans, so confirming their absence from cannabis products is crucial. The number of pesticides that must be tested and their tolerance limits vary from state to state. Without specific methods of regulation from the individual states, EPA (Environmental Protection Agency) guidelines are followed for pesticide residue analysis. For a majority of pesticides (carbamate pesticides), liquid chromatography mass spectrometry (LC-MS) is acceptable and operates much like HPLC but utilizes a different detector and sample preparation. It is desirable to have a LC-MS/MS system or HPLC system with a triple quadrupole (QqQ) mass spectrometer that provides ultra-low detection limits, high sensitivity and efficient throughput. Pesticides that do not ionize well (Chlorinated hydrocarbons, organophosphates, or pyrethroids) in an LC-MS source require the use of a gas chromatography mass spectrometry (GC-MS) instrument. Here too, it is desirable to consider an instrument that utilizes a triple quadrupole mass spectrometer and a headspace autosampler to help maximize efficiency of detection.

Terpene Profile Testing: Terpenes are produced in the trichomes of the cannabis leaves, where THC is created, and are common constituents of the plant’s distinctive flavor and aroma. Terpenes also act as essential medicinal hydrocarbon building blocks, influencing the overall homeopathic and therapeutic effect of the product. The characterization of terpenes and their synergistic effect with cannabinoids are key for identifying the correct cannabis treatment plan for patients with pain, anxiety, epilepsy, depression, cancer and other illnesses. This test is not required by most states, but it is recommended. The instrumentation that is used for analyzing terpene profiles can be GC/MS with headspace autosampler (also used in Residual solvent testing) or GC-MS/MS with an appropriate spectral library. Since residual solvent testing is an analysis required by most states, the instrumentation required for terpene profiling should already be available.

Moisture Content and Water Activity Testing: Moisture can be extremely detrimental to the quality of stored cannabis products. Dried cannabis typically has a moisture content of 5% to 12%. A moisture content above 12% in dried cannabis is prone to fungal growth (mold). Below a 5% moisture content, the cannabis will turn to a dust-like texture. Moisture testing is particularly relevant to flowers, and solid and semi-solid cannabis products.

Microbe, Fungus and Mycotoxin Testing: Mycotoxins are toxic compounds that are naturally produced by certain types of molds (fungi) and can grow on cannabis plants. Mycotoxins can cause a variety of adverse health effects (ranging from acute poisoning to immune deficiency and cancer) and pose a serious health threat to both humans and livestock. Microbial testing is essential to ensure that cannabis users are not being exposed to harmful contaminants, particularly in individuals with a compromised immune system making them susceptible to illnesses arising out of microbial contamination. According to WHO (World Health Organization), consumption of more than 1 mg/kg (1 part per million) of aflatoxin is sufficient to lead to life-threatening aflatoxicosis and liver failure. Alternatively, sustained exposure to lower dosages, on the order of 20-120 μg/kg daily for a period of 1-3 weeks of aflatoxin B1 specifically can also be acutely toxic and potentially lethal. Currently, many laboratories perform total count tests that target large microbial groups that are considered indicator organisms (e.g. aerobic bacteria, coliforms, Enterobacteriaceae, and yeast & mold). Almost all state testing requirements tend to focus on five mycotoxins in particular: aflatoxins B1, B2, G1, G2, and ochratoxin A. Some states require testing for species-specific known human pathogens such as Salmonella, Shiga-toxin producing E. Coli (STEC), and Aspergillus. These pathogen specific tests provide much more useful information in the context of consumer safety. A high-sensitivity LC-MS/MS instrument is recommended to be used to quantitate mycotoxins. Most state testing regulations widely appear to stick to a maximum allowable limit of 20 μg/kg of mycotoxin detected on a sample. However, there is variation in exactly how this limit is applied between states.

Shelf-Life and Stability Testing: Buyers of cannabis products, as with any consumer item, expect product labels to show the shelf-life and recommended storage conditions, especially when used for medicinal purposes.  With enhanced awareness, cannabis users increasingly understand that hemp and cannabis extracts can change with time and environmental conditions (exposure to light, temperature changes, oxygen exposure etc.) leading to degradation and loss of cannabinoids. In this light, testing for shelf-life and stability may be recommended by some state regulatory bodies.

How to ask the right questions when choosing a potential testing lab partner

This article began by referencing current news about regulation and what can go wrong when cannabis products are improperly tested. The fact of the matter is that as a manufacturer or producer, it is your responsibility to do your due diligence and not simply choose a laboratory testing partner based solely on speed, convenience, or price.  Here are the steps you should take when choosing a laboratory testing partner:

  1. The FDA’s motto is Trust but Verify.  Follow this advice by visiting and auditing any potential lab partner.  Get to know the laboratory.
  2. Ask to see and review accreditations and certification documents.  A quality laboratory will have their paperwork in order ready for your review.
  3. Ask for and agree to sign a Quality Agreement.  This defines not only the business relationship but also the quality relationship.  This document should be a binding contract outlining the laboratory’s services and who is responsible for specific tasks.
  4. When it comes to laboratory testing, data integrity is critical and the best way to check for this is to see if the laboratory’s work follows ALCOA, an acronym which means: Attributable, Legible, Contemporaneous, Original, and Accurate.  Every step taken by a laboratory when testing your product should be documented and traceable back to who did it, when did they do it and why. When in doubt, ask questions.

In conclusion, all cannabis products must be tested for their cannabinoid content and several other factors that impact consumer safety, protection for growers, manufacturers and distributors from incurring liabilities due to potential mislabeling. Manufacturers of cannabis products should partner with testing laboratories that are FDA registered and approved, ISO 17025 certified, and conduct tests according to CGMP and well known regulations and standards (such as United States Pharmacopeia), as well as using appropriate state-of-the-art validated instrumentation. Following these guidelines will go a long way in avoiding testing pitfalls, given the current ambiguous regulatory environment.


  1. Valdes-Donoso, P., Sumner, D. A. and Goldstein, R. S. “Costs of mandatory cannabis testing in California”  California Agriculture 73(3-4), 154-160 (2019).

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