Inter-Lab Variation in the Cannabis Industry, Part II: Solutions: Page 2 of 3

June 11, 2019

Improved State Oversight

As of now it is state governments that bear the brunt of regulating the cannabis industry. The fact that the inter-laboratory variation problem exists in multiple states means that no one state government has completely figured out how to regulate cannabis testing properly. Wouldn’t it be great if state regulators and cannabis scientists from around the country got together, harmonized regulations, and agreed on best practices for cannabis analysis? In the absence of federal oversight, it would go a long way towards solving this problem. Until then, individual states could begin by choosing a “golden laboratory” within the state whose methods are trusted enough that it would be the go-to laboratory for any questions about samples analyzed elsewhere. As I have pointed out previously (4), the lack of SRMS in our industry means that true accuracy, or knowing how far away you are from the true value, is impossible to achieve. In this absence, it makes sense to pick a laboratory whose instrument, personnel, and method have been properly vetted and trusted enough to put a stake in a ground and be the “true value” that all other laboratories in a state must compare their results to. Alternatively, state regulators could be more specific in their regulations, calling out specific extraction methods for example that are used industry-wide and known to work.

State personnel should also perform blind round-robin studies, similar to those already published in the literature (5-7), by sending the same sample to multiple labs, tabulating and comparing the results, and publishing them so the public knows who is and who isn’t doing a good job. To be clear, the inter-laboratory variation problem has been observed with cannabis laboratories that are state and International Organization for Standardization (ISO) licensed and certified (5).

This means these certifications by themselves are not sufficient to ensure every laboratory in a state gets similar results on the same sample. This indicates that state governments need to step up their game to solve this problem.

Industry Organizations Need to Speed Up Their Work

At the moment the United States Pharmacopeia (USP), the Association of Official Analytical Chemists (AOAC), and the American Society for Testing and Materials (ASTM) all have committees working on cannabis method and materials standardization. Like anything run by volunteers, progress is steady but can be slow. I would urge these organizations to speed up their process given the danger that the inter-laboratory variation problem poses to our industry and public health. If everyone reading this article volunteered for one of these organizations, the problem will be solved sooner.

Representative Sampling

Briefly, given the inhomogeneity of cannabis samples, particularly plant material, the taking of one aliquot, testing it, and reporting out one set of results is inappropriate. Statisticians tells us that the best way to overcome inhomogeneity is to test multiple aliquots and average the results (3).

I realize that testing multiple aliquots is time-consuming and expensive, but it is the only way to obtain representative data on our samples and begin to chip away at the problem of inter-laboratory variation.

Perhaps state regulators can step in here and require more than one aliquot of each sample be tested, particularly for failed samples or samples close to action limits. Also, laboratories need to consider methods other than chromatography such as infrared spectroscopy (7) that are faster, cheaper, easier, and more readily lend themselves to analyzing multiple aliquots.

  1. B.C. Smith, Cannabis Science and Technology 1(3),10-12 (2018).
  2. B.C. Smith, Cannabis Science and Technology 1(4),12-16 (2018).
  3. B.C. Smith, Cannabis Science and Technology 2(1),14-19 (2019).
  4. B.C. Smith, Cannabis Science and Technology 2(2), 12-17 (2019).
  5. B.C. Smith, P. Lessard, and R. Pearson, Cannabis Science and Technology 2(1), 48-53 (2019).
  6. B. Young, The Seattle Times January 5, 2016.
  8. M. Starks, Marijuana Chemistry (Ronin Publishing, Oakland CA, 1977).
  9. J. Fairbairn, J. Liebmann, and M. Rowan, Journal of Pharmacy and Pharmcacology, 28(1) (1976).
  10. I. Trofin, G. Dabija, D. Vaireanu, and L. Filipescu, Revista de Chimie (Bucharest), 63(293) (2012).
  11. C. Lindholst, Australian Journal of Forensic Sciences 42(181) (2010).
  12. B.C. Smith, Terpenes and Testing, Nov.-Dec. pg. 48 (2017).
  13. B.C. Smith, Terpenes and Testing, Jan.-Feb. pg. 32 (2018).
  14. J. Strull, private communications.


Brian C. Smith, PhD, is Founder, CEO and Chief Technical Officer of Big Sur Scientific in Capitola, California. Dr. Smith has more than 40 years of experience as an industrial analytical chemist having worked for such companies as Xeros, IBM, Waters Associates, and Princeton Instruments. For 20 years he ran Spectros Associates, an analytical chemistry training and consulting firm where he improved their chemical analyses. Dr. Smith has written three books on infrared spectroscopy, and earned a PhD in physical chemistry from Dartmouth College.


How to Cite This Article
B.C. Smith, Cannabis Science and Technology 2(3), 10-14 (2019)