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Why is Cannabis Testing Important?

By Tiffany Quinn

Published: Jul 04, 2022   
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Compliance and oversight are key to protecting the cannabis industry and encouraging consumers to avoid the illegal, unregulated market. As cannabis legalization continues, so has the demand for cannabis testing services to ensure that medical and recreational cannabis sold on the market meets quality and safety requirements for consumption and is free from harmful contaminants. However, there are several challenges for cannabis testing – particularly in the United States where testing requirements vary across states and depend on the type of cannabis that the crop or product is derived from.1

This article will explore the importance of cannabis testing with reference to the common testing methods used and how labs are overcoming some of the challenges faced in the industry.

What are cannabis testing labs?

Put simply, cannabis testing labs are responsible for quality control. Cannabis and cannabis-derived products purchased from a licensed facility are subject to various tests which screen samples for various components that influence product quality and safety. Most cannabis testing labs conform to ISO/IEC 17025:2017, which refers to the “General requirements for the competence of testing and calibration laboratories.” Others go further to comply with standards outlined by AOAC International and ASTM International. All cannabis testing labs must be equipped with modern, sensitive analytical instruments and qualified technicians and analysts who are trained in each testing method. 

As the industry continues to grow and cannabis labs use data to monitor lab performance, they are also becoming important for:

  • Building trust with consumers and healthcare providers
  • Mitigating risks in a rapidly expanding market
  • Focusing on superior products

Another important aspect of cannabis testing is understanding why testing failures may occur. Lydia Abernethy is a senior science consultant at Steep Hill Labs and current chief executive officer at Rain Changes Everything LLC, a cannabis crop consulting company. Her role is to help analytical laboratories and cultivating companies mitigate and manage testing failures. Here’s what she had to say on the issue of testing failures in her recent Teach Me in 10 for Analytical Cannabis:

Analytical Testing and Cannabis Cultivation With Lydia Abernethy. Watch the full Teach Me in 10 episode here.

What is cannabis tested for?

Regulatory testing generally requires potency measurements so the product can be labelled to inform the consumer. Samples are also screened for residual contaminants such as pesticides, heavy metals, processing chemicals, and microbes or microbial by-products. This section will examine the various testing methods that exist to achieve this.

Potency testing

Potency testing investigates the cannabinoid and terpenoid content to determine how much CBD and THC a product contains. Gas chromatography coupled with a flame ionization detector (GC-FID) is a fast solution for potency testing, which enables accurate quantification of all the organic chemical species present in a sample. However, liquid chromatography is a more direct method for full cannabinoid profiling, since an analyst can also measure the amount of cannabidiolic acids in a sample. The two most commonly used methods are high-performance liquid chromatography coupled with a diode array detector (HPLC-DAD) and liquid chromatography time-of-flight mass spectrometry (LC-TOF-MS). Unlike a standard UV-vis detector, HPLC-DAD simultaneously gathers data over a range of wavelengths. 

Dr Holly Johnson, chief science officer at American Herbal Products Association told Analytical Cannabis in 2020 that “HPLC-DAD has gained popularity for cannabinoid analysis for a variety of reasons including short run times and low limits of quantification for each analyte.”

Figure 1. A comparison between the structure of tetrahydrocannabinol (THC) and cannabidiol (CBD). Over 100 cannabinoids have been isolated from the cannabis plant. Many of these cannabinoids are linked to several medicinal benefits.

Pesticide testing
Although pesticide use for agriculture is usually regulated, there are still many countries and territories that consider cannabis an illegal drug. For example, despite being legal for recreational and medical uses across dozens of states, cannabis is still illegal at the federal level in the United States. As a result, the US Environmental Protection Agency (EPA) has not approved a list of pesticides for cannabis. While pesticide testing subsequently varies across labs,2,3 the general protocol involves an extraction step (to capture pesticides present in the sample), a clean-up step (to remove pigments or interferences that may affect results), and analysis (liquid or gas chromatography with tandem mass spectrometry (LC/MS/MS or GC/MS/MS) is typically used). QuEChERS (quick, easy, cheap, effective, rugged, and safe) is a popular solid phase extraction method used to extract pesticides. During analysis, some compounds are more amenable to GC over LC, therefore many labs will use a combination of both techniques to ensure that their workflow is sensitive to all the required compounds. 

Microbial testing

In addition to testing for common bacteria such as E. Coli and Salmonella, cannabis is also screened for yeast, mold, and fungi. Culture-based detection is a straightforward technique that has been the gold standard since the 1900s, but one that requires specific nutrients and environmental conditions. The emergence of molecular diagnostic tools bypasses the need to culture. For example, quantitative polymerase-chain-reaction (qPCR) analysis is a high-tech approach that enables analysts to collect all the genomes present in a sample and amplify DNA segments. As a result, the genetic barcode can be used to identify the microbial components present in the sample.4,5 

Talking to Analytical Cannabis in 2019, Amanda Horodyski, associate laboratory director at Atlantic Test Labs Inc, said, “Traditional culture plating methods can take up to seven days, in contrast, a PCR method takes around two days, including the incubation period.” 

“Culture-based techniques often result in false positives because plating is easier to contaminate and requires a trained microbiologist on staff in order to distinguish between yeast and bacteria species.”

Figure 2. Three common microbial contaminants found on cannabis plants.

When left to proliferate, molds and fungi release harmful mycotoxins. Qualitative testing strips can be used to screen for mycotoxins; they exploit the natural reaction between antibodies and mycotoxins by producing a color change in their presence. By contrast, quantitative strips use the same natural reaction, but give a digital readout for the quantity of mycotoxin detected. Most formal cannabis testing labs will use immunoaffinity column chromatography to separate the sample into its constituent components before analysis using a bench-top fluorometer. However, larger cannabis testing labs will use ultra-performance LC/MS/MS (UPLC/MS/MS) to enhance accuracy and save on time and money. 

Heavy metal testing

Heavy metal contamination can occur as cannabis plants grow and absorb them from the surrounding soil. These metals are known to be highly toxic as the human body is unable to efficiently remove them after exposure, causing accumulation over time. The four key metals of interest include cadmium (Cd), arsenic (As), lead (Pb) and mercury (Hg). Heavy metal testing is usually done using one of three techniques:

  • Atomic absorption (AA): A simple, low-cost technique which measures the concentration of certain analytes by analyzing the wavelengths of light absorbed by gaseous free atoms within the sample. 
  • Inductively coupled plasma optical emission spectroscopy (ICP-OES): A more efficient method than AA, which excites the elements in a sample and measures the brightness and wavelengths of light that they subsequently emit.
  • Inductively coupled plasma mass spectrometry (ICP-MS): Works by ionizing the elements before feeding them into the mass spectrometer for analysis based on their mass-to-charge ratios. This method is popular amongst labs with a larger budget; it is faster, has a high throughput and is the most sensitive technique. 

Figure 3. The four most common heavy metals found in cannabis. Each of these have been reported to have significant short- and long-term effects on the body.

What are the challenges for cannabis testing?

There are several challenges that make cannabis testing difficult. This section will examine them in more detail.


State-mandated compliance testing for cannabis products has resulted in industry-wide protection of public health. However, the lack of standardization presents challenges and opportunities with respect to what is not monitored. Additionally, producers of edibles and infused beverages certainly face their own unique challenges.1 Most laboratories must balance regulatory compliance with customer needs and scientific integrity, which often results in some form of compromise.6 At the Analytical Cannabis Expo East Online 2020 in October, Josh Smith, CEO & chief scientist at Premium CBD Labs, discussed the impact of the variations in microbial testing across the US:

Variations in Microbial Testing Requirements Across the US. Watch the full presentation here.

Despite the lack of harmonization, the industry is evolving to towards a more quality-centric operation. For example, over the past few years, the leading US testing standards organization has been proposing and publishing new standards for cannabis testing, processing, cleaning, and transporting. Likewise, cannabis companies are starting to embrace the benefits of CGMPs, purpose-built laboratory informatics that support regulatory compliance, and advanced data practices that maintain quality and meet the growing complexity in the market.

Capital expenses

A successful laboratory should strive to have highly experienced laboratory personnel as well as high-tech instrumentation that complies with regulatory standards. Such capital expenses will vary depending on a lab’s financial capacity and the testing requirements, but a general cost estimate is between $2-3 million to set up a cannabis testing lab.6 Additionally, once running, labs should purchase a good quality system to mitigate long-term risk, although this can be expensive to maintain due to the expenses of personnel, audits, and proficiency tests. It also impacts capacity due to the number of quality control samples required for each batch and any re-runs that must be performed due to non-conformance.

Laboratory shopping

Cannabis labs exist to act as public safety agents, which ensure that products are safe for consumption and packaged with labels that clearly outline the product’s components.7 Yet lab shopping – whereby growers and distributors shop around for the lab that gives them the best results – is becoming a serious issue as more labs open and the cost of switching labs is negligible.8 Misreporting pesticides is another significant issue that is not only harmful to consumers, but hinders the industry overall. The implications of laboratory shopping include potency inflation, extremely low compliance failure rates, and data integrity issues.9


Cannabis testing labs support consumer safety and product quality by limiting the occurrence of residual pesticides, processing chemicals and microbials. The continually evolving landscape, makes things confusing for those involved in cannabis production and processing and creates challenges for those in the analytical testing world, who must understand and develop methods to comply with various and ever-changing regulatory requirements. As regulations continue to change, more testing data is acquired and testing programs are evaluated, the industry must look to other established and regulated industries (pharmaceutical, food, and environmental) and adopt a collective approach to cannabis testing to ensure its continued growth, credibility, and acceptance.1


  1. Goldman S, Bramante J, Vrdoljak G et al. The analytical landscape of cannabis compliance testing. Journal of Liquid Chromatography & Related Technologies. 2021;44(9-10):403-420. doi:10.1080/10826076.2021.1996390 
  2. Seltenrich N. Into the Weeds: Regulating Pesticides in Cannabis. Environ Health Perspect. 2019;127(4):042001. doi:10.1289/ehp5265
  3. Countries Where Weed Is Illegal 2022. World Population Review. https://worldpopulationreview.com/country-rankings/countries-where-weed-is-illegal. Published 2022. Accessed June 23, 2022.
  4. Fredericks D, Relman D. Sequence-based identification of microbial pathogens: a reconsideration of Koch's postulates. Clin Microbiol Rev. 1996;9(1):18-33. doi:10.1128/cmr.9.1.18
  5. Wetterstrand, M.S. K. DNA Sequencing Costs: Data. Genome.gov. https://www.genome.gov/about-genomics/fact-sheets/DNA-Sequencing-Costs-Data. Published 2022. Accessed June 23, 2022.
  6. Audino, PhD, S. Facing Key Challenges in the Cannabis Testing Industry. Lab Manager. https://www.labmanager.com/big-picture/ensuring-quality-in-cannabis-and-hemp-testing/facing-key-challenges-in-the-cannabis-testing-industry-26939. Published 2022. Accessed June 23, 2022.
  7. Swider J. Lab Shopping: Highlighting the Need for Checks and Balances in Cannabis. Cannabis Industry Journal. https://cannabisindustryjournal.com/column/lab-shopping-highlighting-the-need-for-checks-and-balances-in-cannabis/. Published 2021. Accessed June 23, 2022.
  8. Downs D. 40% THC Flower?! How Lab Shopping and THC Inflation Cheat Cannabis Consumers. Leafly. https://www.leafly.com/news/strains-products/lab-shopping-thc-inflation-marijuana-2019-leafly-review. Published 2019. Accessed June 23, 2022.
  9. Swider J. Ethics or Profits?. The Cannabis Scientist. https://thecannabisscientist.com/testing-processing/ethics-or-profits. Published 2022. Accessed June 23, 2022.

Tiffany Quinn

Custom Content Manager


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