Journal:Leaner and greener analysis of cannabinoids

Full article title	Leaner and greener analysis of cannabinoids
Journal	Analytical and Bioanalytical Chemistry
Author(s)	Mudge, Elizabeth M.; Murch, Susan J.; Brown, Paula N.
Author affiliation(s)	British Columbia Institute of Technology, University of British Columbia
Primary contact	Email: Paula underscore brown at bcit dot ca
Year published	2017
Volume and issue	409(12)
Page(s)	3153–63
DOI	10.1007/s00216-017-0256-3
ISSN	1618-2650
Distribution license	Creative Commons Attribution 4.0 International
Website	https://link.springer.com/article/10.1007%2Fs00216-017-0256-3
Download	https://link.springer.com/content/pdf/10.1007%2Fs00216-017-0256-3.pdf (PDF)

Abstract

There is an explosion in the number of labs analyzing cannabinoids in marijuana (Cannabis sativa L., Cannabaceae); however, existing methods are inefficient, require expert analysts, and use large volumes of potentially environmentally damaging solvents. The objective of this work was to develop and validate an accurate method for analyzing cannabinoids in cannabis raw materials and finished products that is more efficient and uses fewer toxic solvents. A method using high-performance liquid chromatography (HPLC) with diode-array detection (DAD) was developed for eight cannabinoids in Cannabis flowers and oils using a statistically guided optimization plan based on the principles of green chemistry. A single-laboratory validation determined the linearity, selectivity, accuracy, repeatability, intermediate precision, limit of detection, and limit of quantitation of the method. Amounts of individual cannabinoids above the limit of quantitation in the flowers ranged from 0.02 to 14.9% concentration (w/w), with repeatability ranging from 0.78 to 10.08% relative standard deviation. The intermediate precision determined using Horwitz ratios (HorRat) ranged from 0.3 to 2.0. The limits of quantitation (LoQs) for individual cannabinoids in flowers ranged from 0.02 to 0.17% w/w. This is a significant improvement over previous methods and is suitable for a wide range of applications, including regulatory compliance, clinical studies, direct patient medical services, and commercial suppliers.

Keywords: green chemistry, single-laboratory validation, Cannabis, cannabinoids, medical marijuana

Introduction

The modern cannabis market is in a period of dramatic flux. In the United States, cannabis is classified as a Schedule I drug; however, eight U.S. states have legalized marijuana for recreational use, and 28 states have allowed medical marijuana on the basis of evidence of anxiolytic, analgesic, sedative, anticancer, and appetite stimulation effects. Regulations regarding Cannabis spp. vary globally. The Netherlands, Uruguay, and Portugal have decriminalized possession. In Canada, cannabis is a Schedule II controlled substance, but regulations have allowed production for medical purposes through licensed producers and personal production licenses. Canadian production of commercial products must take place in a facility using good manufacturing practices, and products must be assayed for the presence and quantity of Δ9-tetrahydrocannabinol (Δ9-THC), Δ9-tetrahydrocannabinolic acid (THCA), cannabidiol (CBD), and cannabidiolic acid (CBDA), using validated analytical methods. In total, more than 100 cannabinoids in 11 subclasses have been characterized in cannabis and are concentrated in the glandular trichomes of the female inflorescences. Other cannabinoid classes include cannabigerol (CBG), cannabichromene (CBC), and cannabinol (CBN) (Fig. 1). The cannabinoids occur primarily in acid form, with neutral cannabinoids formed during drying, storage, and decarboxylation during smoking. Δ9-THC, the main psychoactive cannabinoid, can be over 20% by weight in specially bred cannabis strains. CBD, known for its anti-inflammatory activity and antagonism of Δ9-THC-induced anxiety, can range from below 0.5% up to 6.5% by weight.

Fig. 1 Structures for the main neutral cannabinoids found in Cannabis flowers

There are a significant number of analytical methods to quantify cannabinoids available, many of which do not provide sufficient validation data to establish the method performance and reliability. Without this information, there is a possibility that the methods are not fit for purpose. The solvent composition, mass-to-solvent ratio, extraction technique, and time vary considerably between methods. Separations of cannabinoids use different mobile phases, columns, and gradients, and given the number of minor cannabinoids present in authentic materials, there is a possibility for coelution of peaks and inaccurate quantitative results. Rigorous validation procedures are necessary to ensure that the results of any analytical method are reliable. Without this data on method performance, the final method may not meet the needs of the users who adopt it for routine use, therefore producing inaccurate information pertaining to the products that people are using for the treatment of medical conditions. The speed with which regulations have changed and the nature of the rapidly expanding cannabis marketplace have created increased pressure for fast, safe, simple, and accurate analysis of phytochemicals to meet the demands of high-throughput laboratories and rapid release of finished products.

Notes

This presentation is faithful to the original, with only a few minor changes to presentation. Some grammar and punctuation was cleaned up to improve readability. In some cases important information was missing from the references, and that information was added.