nterview Conducted by Jason S. Lupoi, Ph.D.
Cannabis is an extremely complex plant, from its chemical wealth, including over 500 ingredients [1], to the varied and diverse ways that it provides medicinal prosperity to humanity [2]. While some people might argue that the regulations in place for the cannabis industry are too strict, especially when compared to other industries, the need to ensure that tainted products do not make it to market is no less important.
Cannabis analytical laboratories are the final line of defense in making sure that products are uncontaminated, compliant (if considering hemp industry products), and accurately labeled. They test for things that can harm consumers such as mycotoxins, pesticides, or heavy metals. They may conduct homogeneity testing on edibles to ensure an equal distribution of delta-9-tetrahydrocannabinol (THC) throughout the product so that when a consumer breaks a piece off, there are no surprises.
The aforementioned complexity of the plant, including many isomers or at least molecules that are structurally similar, added to the intricacy of downstream products like chocolate bars, can complicate the analytics. Toss in ancillary product components like rolling papers, vape carts, and food-based ingredients, and the need to make sure that analytical methods are sensitive for detecting molecules that shouldn’t be there (i.e., aflatoxin, lead, myclobutanil), and it’s easy to see that this is no small undertaking.
I recently spoke with Josh Wurzer, president and co-founder of SC Labs, to learn more about what can go wrong during analytical method development and testing, and how a lab can excel past these challenges.
Choosing Equipment and Validating Methods
Jason S. Lupoi, Ph.D.: When someone is selecting lab equipment, what are the main things they should consider?
Josh Wurzer: They should be focused, foremost, on selecting equipment that will clearly meet the method performance criteria for the particular assays they are trying to perform. Beyond that, much like anything else, the various manufacturers of analytical instrumentation and lab equipment all have different features and services that may appeal to your vision of how your laboratory will operate. Of course, cost is oftentimes the primary consideration. There are a lot of factors that go into selecting laboratory equipment.
JSL: When a method is created for a specific matrix, how important is it to re-validate the method when a new matrix is introduced? For example, the method is generated on flower, but the lab needs to measure edibles too. How do you suggest best matching the matrix on a food, like a THC-infused pizza or brownie?
JW: It depends on the method. Oftentimes, a particular sample prep or analysis is effective for several different matrices; other times, a method needs to be adjusted in different ways for even slight variations in a matrix. The key is to validate the method and to have a clear picture of how it performs under various conditions including stress testing it in a production environment before taking it live. Through this process, the lab should have a clear understanding of how the method performs and be able to adjust or correct for various matrices.
Isomers and Contaminants
JSL: Cannabis analytics includes lots of isomers. What equipment have you found to be important in being able to resolve isomers, and what are a couple of experimental methods/options you could point to regarding how to better resolve these species?
JW: Depending on the instrumentation, there are various tools in the toolbelt to better resolve similar compounds. For example, when using HPLC [high-performance liquid chromatography] or GC [gas chromatography], regardless of detectors, we can adjust the mobile phase, play with column size or chemistry, or adjust things like flow rates and temperatures to tease out better separation in the chromatography. Of course, with HPLCs and GCs, the columns and mobile phases are very different, and there are several more things we can do to improve separation that are unique to each technique. But, in general, this is what method development is for; you build upon the previous work to develop new methods and then improve them when needed.
JSL: SC Labs evaluated rolling papers for contaminants including heavy metals and pesticides. What other types of ancillary equipment have you evaluated, are planning to evaluate, or think should be evaluated?
JW: Heavy metal contamination can really come from anywhere, especially in an industrial environment. We have traced contamination back to vape carts, plastics, Styrofoam, and just plain dust from the environment.
Plating or PCR?
JSL: There seems to be a debate over microbial testing methods: plating versus quantitative polymerase chain reaction (qPCR). What’s your take on this?
JW: That depends on the requirements of the assay. Comparing them is a little like comparing a pair of pliers and a wrench. While either might be able to accomplish a particular task, usually one or the other is going to clearly be the better tool depending on the job. For example, PCR and other molecular techniques are generally, when designed well, much more specific than culture-based methods, giving fewer false positives. PCR can also be very sensitive. So if I were looking to detect a single copy of a specific pathogen like Aspergillus flavus, I’d probably look to use a PCR-based technique. However, culture-based methods are better at distinguishing between viable and non-viable organisms, and they are great for looking at broad classes of indicator organisms. There is also a long history of performing these tests on food items, so we have standards established for what is acceptable and not acceptable that we can transfer between similar products. So, if I was looking to determine the overall microbiological load on an infused product to determine its shelf life, I’d probably look to do a standard culture-based test like Total Yeast and Mold or Total Aerobic Plate Count.
Working With Your Lab
JSL: If a cannabis grower/processor wants to employ in-house testing to monitor processes in real time, how do you suggest they work with their lab of choice to remove as many variables as possible, such that the analytics can be actively compared, apples to apples?
JW: We try to work with our customers who have in-house labs to make sure our methods are aligned. Our customers appreciate the help and transparency. If the laboratory is cagey or defensive about their methods, that should be a red flag. If you do have an in-house lab, you can still test your laboratory to see if your measurements are similar when testing the same products. However, the laboratory should be willing to be your partner in this process.
JSL: What do you see as the up-and-coming methods/instruments/techniques for cannabis analytical testing?
JW: I think that will come with new tests. Right now, we are focusing on improving our multistate hemp panels. We are the only lab that I am aware of that has a complete suite of test panels accredited to ISO 17025 that address regulations in all 50 states for hemp. That has been a really time-consuming process as new states are coming on-line all the time with requirements for hemp testing and we haven’t been able to stop development on any of the tests just trying to keep up. Beyond that, I think you will see more of a continued evolution of techniques and many new tests to continue to help growers and processors improve their products and increase efficiency.
JSL: Lastly, what are the most common misconceptions surrounding cannabis testing, and how do we move beyond them?
JW: I think a lot of people don’t necessarily understand everything that goes into doing some of the tests we perform. Oftentimes, we are measuring the equivalent of a few drops of food coloring in a swimming pool and it still amazes me how precise we can be in making those measurements. However, there are always limitations to any analytical techniques, and it is immeasurably important to have a rigorous quality control system in place to ensure your measurements are reliably accurate and repeatable. This is why it is important for clients of testing labs to vet the quality control system the lab has in place as much as they consider things like turnaround time and cost. A laboratory should welcome you to audit this part of their business, as it is essential to the ultimate quality of the data you are receiving from them.
Editor’s note, October 2026: This conversation, conducted by Jason S. Lupoi, Ph.D., was published in August 2021. Josh Wurzer co-founded SC Labs, and its most recent profile of him (January 2025) lists him as co-founder and Chief Compliance Officer; since 2024 he has also served on the board of the National Cannabis Industry Association.[3,4] SC Labs has grown since the interview: it combined with Agricor and Botanacor Laboratories in 2022 and acquired Arizona’s C4 Laboratories in 2023, and it still trades as SC Labs.[5,6] The rules around labs have moved too. California has required every licensed lab to use a standardized cannabinoids test method for dried flower and non-infused pre-rolls since January 2024,[7,8] and in 2026 Colorado regulators began weighing an end to manufacturers choosing which samples they send to labs.[9] ISO/IEC 17025:2017, the accreditation standard Wurzer refers to, remains current; ISO reviewed and confirmed it in 2023.[10] His answers above are kept exactly as given; the section that follows sets out what the evidence shows now.
What the Evidence Says
Wurzer’s closing point, that clients should vet a lab’s quality control as carefully as its price, is the one the evidence supports most strongly. Most of the other failure modes he describes have been measured since 2021, and in a few places the picture has moved.
Labs disagree, often in consistent directions. When the US National Institute of Standards and Technology (NIST) sent two hemp oils to laboratories in 2021, the spread of delta-9 THC results across labs was only 2 to 3%. Yet more than half of the participating labs fell outside NIST’s tolerance range, and labs that read low on one oil tended to read low on the other. The authors note that trends of this type often indicate a calibration bias.[11] A 2022 NIST round on moisture, the measurement behind every dry-weight result, found 86% of lab means outside NIST’s tolerance, with results varying widely by drying method.[12] The first exercise was educational, with no pass or fail grades, but both show why Wurzer’s advice to compare in-house and partner-lab results on the same products is sound.
Potency is where it shows. An analysis of more than 300,000 Washington test results found systematic differences between labs: the median THC in comparable flower ranged from 17.7% at the lowest-reporting lab to 23.2% at the highest, even after accounting for grower, strain and test date.[13] A 2023 Colorado study found that about 70% of 23 retail flower samples contained more than 15% less THC than their labels claimed.[14] Our article on why two labs give different THC numbers covers this literature in detail. It is also why California stopped leaving the cannabinoid method to each lab: under the standardized method, only 18 of the state’s 38 licensed labs were compliant as of January 8, 2024.[8]
Matrices and isomers are real problems. Wurzer’s point that a method validated on flower may not hold for an edible is reflected in AOAC INTERNATIONAL’s method standards, which set a separate performance requirement for cannabinoids in chocolate.[15] His point about resolving similar compounds has grown sharper with the hemp-derived market. In the NIST exercise, THCA and delta-8 THC results scattered widely, partly because of possible interferences and misidentifications, and one cannabinoid could not be quantified reliably at 220 nm because of a co-eluting compound.[11] A 2021 analysis of delta-8 vapes found that none of 27 products was accurately labeled and all contained synthesis byproducts, including other THC isomers.[16]
Metals from hardware. Wurzer traced metals to vape carts and plastics. A 2025 scoping review agrees that heating coils, battery contacts and mouthpieces are recurring sources, that lead, nickel, chromium and copper leach more at higher temperatures, and that testing should extend beyond the usual four metals.[17]
Plating or PCR. His “pliers and wrench” answer holds. One sequencing study found that culture-based yeast and mold tests shifted the microbial profile of cannabis samples: Aspergillus grew poorly, while some bacteria grew readily. Most of its authors worked for the maker of the qPCR test in the study, which is worth weighing.[18] For more on the trade-off, see our comparison of qPCR and plating.
For where these failure modes sit in the wider testing picture, start with our complete guide to cannabis testing. Our guide to how cannabis potency testing works covers the methods, and our guide to laboratory certificates of analysis explains what the final report does and does not certify.
References
[1] Andre CM, Hausman JF, Guerriero G. Cannabis sativa: The plant of the thousand and one molecules. Front Plant Sci. 2016;7:19. [journal impact factor = 4.407; times cited = 448] [2] Russo EB. History of cannabis and its preparations in saga, science, and sobriquet. Chem Biodivers. 2007;4(8):1614-1648. [journal impact factor = 2.408; times cited = 291] [3] SC Labs. Josh Wurzer: The Realities of Cannabis Testing and Industry Integrity. January 11, 2025 (repost of a Ganjapreneur interview). [4] National Cannabis Industry Association. NCIA Welcomes New and Returning Members to its Board. January 10, 2024. [5] SC Labs. Agricor, Botanacor and SC Laboratories Combine to Form Leading Cannabis and Hemp Testing Laboratory Platform in North America. February 22, 2022. [6] SC Labs. SC Labs Expands into Arizona with the Acquisition of C4 Laboratories. April 24, 2023. [7] California Department of Cannabis Control. Standard Cannabinoids Test Method and Standardized Operating Procedures (rulemaking). [8] Lange T. Only 18 of 38 labs compliant to test California’s cannabis flower under new rule. Cannabis Business Times. January 11, 2024. [9] Osher C, Wyloge E. Colorado Marijuana Regulators Consider Major Changes to How Labs Test for Contaminants. The Denver Gazette / ProPublica. February 11, 2026. [10] International Organization for Standardization. ISO/IEC 17025:2017 General requirements for the competence of testing and calibration laboratories. [11] Abdul-Rahman M, Phillips MM, Wilson WB. Cannabis Quality Assurance Program: Exercise 1 Final Report. NIST IR 8385. July 2021. doi:10.6028/NIST.IR.8385 [12] Barber CA, Bryan Sallee CE, Burdette CQ, Kotoski SP, Phillips MM, Wilson WB, Wood LJ. Cannabis Laboratory Quality Assurance Program: Exercise 2 Moisture Final Report. NIST IR 8449. November 2022. [13] Jikomes N, Zoorob M. The cannabinoid content of legal cannabis in Washington State varies systematically across testing facilities and popular consumer products. Sci Rep. 2018;8:4519. doi:10.1038/s41598-018-22755-2 [14] Schwabe AL, Johnson V, Harrelson J, McGlaughlin ME. Uncomfortably high: testing reveals inflated THC potency on retail Cannabis labels. PLoS One. 2023;18(4):e0282396. doi:10.1371/journal.pone.0282396 [15] Coates S. AOAC INTERNATIONAL — At a Glance. AOAC Research Institute; May 31, 2019. [16] Meehan-Atrash J, Rahman I. Novel Δ8-tetrahydrocannabinol vaporizers contain unlabeled adulterants, unintended byproducts of chemical synthesis, and heavy metals. Chem Res Toxicol. doi:10.1021/acs.chemrestox.1c00388 [17] Gaur S, Agnihotri R. Heavy metals in cannabis vapes and their health implications: a scoping review. Sci World J. 2025;2025:9529544. doi:10.1155/tswj/9529544 [18] McKernan K, Spangler J, Helbert Y, Lynch RC, Devitt-Lee A, Zhang L, Orphe W, Warner J, Foss T, Hudalla CJ, Silva M, Smith DR. Metagenomic analysis of medicinal Cannabis samples; pathogenic bacteria, toxigenic fungi, and beneficial microbes grow in culture-based yeast and mold tests. F1000Res. 2016;5:2471. doi:10.12688/f1000research.9662.1Last updated October 2026 · Originally published August 2, 2021.
