Leveraging Selectivity and Efficiency to Take the Strain Out of LC–UV Method Development for Cannabinoid Profiling

November 12, 2018
Abstract / Synopsis: 

More than 100 cannabinoids have been isolated from cannabis in addition to the five most commonly tested: ∆9-tetrahydrocannabinol (∆9-THC), ∆9-tetrahydrocannabinolic acid (THCA), cannabidiol (CBD), cannabidiolic acid (CBDA), and cannabinol (CBN). Although many methods have been published that show the separation of these major cannabinoids, most do not take into account the possibility of interference from minor cannabinoids. This interference is most problematic in concentrates where minor cannabinoids can be enriched to detectable levels. Additionally, some terpenes absorb ultraviolet (UV) light at the same wavelength as cannabinoids, which can result in an additional source of interference. In this study, the liquid chromatography (LC)–UV separation of 16 cannabinoids of interest was performed while the potential impact from minor cannabinoids and terpenes on reported potency values was monitored. The method was applied to commercially available CBD oils that have recently become suspect because of inaccurate label claims.

Just as consumers rely on nutrition facts labels on food for making informed choices about their diets, labels on cannabis products are intended to provide critical information for accurate dosing. Consumer confidence in labeling claims can be shattered by reports of inaccuracies. A recent study published by the Journal of the American Medical Association showed that of 84 cannabidiol (CBD) products purchased online, only 31% were accurately labeled (1). This labeling problem is alarming since cannabinoids such as CBD and ∆9-tetrahydrocannabinol (∆9-THC) have been found to be very effective for the treatment of various medical disorders; however, accurate dosing is required for positive patient outcomes. As examples, CBD was determined to be an effective treatment for those suffering from treatment-resistant epilepsy while ∆9-THC has been found to be an effective treatment for pain when coadministered with reduced doses of opioids (2,3). Whether labeling inaccuracies stem from inadequate analytical methods, instability of formulations, or surreptitious laboratory practices, all result in the same potentially negative impact to the health and safety of consumers.

Although the state of analytical testing in the cannabis industry has improved since the inception of legalized medical cannabis, there are still many opportunities to update existing methods in this dynamic market. Historically, interest in cannabinoids typically focused on THC, CBD, and their carboxylated forms, but the analysis of more-abundant minor cannabinoids is starting to gather momentum. Testing laboratories most frequently use liquid chromatography (LC)-based techniques paired with ultraviolet (UV) detection for cannabinoid profiling because of its low initial cost, ease of use, and robustness. Because UV detection is limited in its spectral deconvolution abilities, chromatography plays a critical role in not only cannabinoid identification, but also accurate quantitation. The demands on the analytical column are only made more difficult considering the complexity of the matrix. Cannabis is a complex matrix that contains more than 100 cannabinoids as well as hundreds of additional components including terpenes, fatty acids, sugars, flavonoids, and pigments (4). The introduction of cannabis concentrates into additional matrices to create cannabis-infused products further complicates analysis. If product labels are to accurately reflect cannabinoid content, the complete sample composition must be considered in developing a robust and accurate analytical method. Herein, the process of developing a complete workflow solution for the analysis of cannabinoids is discussed with emphasis on LC–UV conditions, sample preparation strategies, method applications, and high-throughput enabling technologies.

  1. M.O. Bonn-Miller, M.J.E. Loflin, B.F. Thomas, J.P. Marcu, T. Hyke, and R. Vandrey, JAMA, J. Am. Med. Assoc. 318, 1708–1709 (2017).
  2. O. Devinsky, E. Marsh, D. Friedman, E. Thiele, L. Laux, J. Sullivan, I. Miller, R. Flamini, A. Wilfong, F. Filloux, M. Wong, N. Tilton, P. Bruno, J. Bluvstein, J. Hedlund, R. Kamens, J. Maclean, S. Nangia, N. Shah Singhal, C.A. Wilson, A. Patel, and M. Roberta Cilio, Lancet Neurol. 15, 270–278 (2016).
  3. S. Nielsen, P. Sabioni, J.M. Trigo, M.A. Ware, B.D. Betz-Stablein, B. Murnion, N. Lintzeris, K. Eng Khor, M. Farrell, A. Smith, and B. Le Foll, Neuropyschopharmacology 42, 1752–1765 (2017).
  4. M. ElSohly, W. Gul, in Handbook of Cannabis,1st Ed., R.J. Pertwee, Ed. (Oxford University Press, Oxford, United Kingdom, 2014), pp. 3–22.
  5. California Code of Regulations, Title 16, Division 42, “Chapter 6, Section 5724 – Cannabinoid Testing,” (Adopted May 5, 2018; Effective June 6, 2018), p. 105.
  6. Code of Colorado Regulations, 1 CCR 212-1, “Section M 1503 – Medical Marijuana Testing Program – Potency Testing,” (Adopted February 21, 2018; Effective February 21, 2018), pp. 218–221.
  7. E.M. Mudge, S.J. Murch, and P.N. Brown, Anal. Bioanal. Chem. 409, 3153–3163 (2017).
  8. J. De Vos, K. Broeckhoven, and S. Eeltink, Anal. Chem. 88, 262–278 (2016).

Justin Steimling is an Applications Manager, LC Solutions at Restek Corporation in Bellefonte, Pennsylvania. Direct correspondence to: [email protected]

How to Cite This Article

J. Steimling, Cannabis Science and Technology 1(4), 30-35 (2018).