The Application Notebook
In the United States, the increasing acceptance of medical and recreational cannabis at the state level has created a need for accurate, precise, and efficient analysis of cannabinoids in marijuana flower, extracts, and formulated products. At the same time, the lack of federal recognition of marijuana for either recreational or medical purposes has effectively decentralized the development of analytical approaches for determination of cannabinoid content in these products, thereby creating a significant need for development of reliable and robust analytical protocols.
This application note shows the fast and simple analysis of nine cannabinoids of interest using an Agilent 1260 Infinity HPLC in an entry level setup. Results obtained from actual cannabis samples were cross validated on another system (LC–MS/MS) using UHPLC separation techniques.
In the cannabis plant, the two major cannabinoids of interest, Δ-9-Tetrahydrocannabinol (THC) and Cannabidiol (CBD) are primarily found in their acid forms (THCA and CBDA respectively; Figure 1). Because the acid forms of these secondary metabolites generally have diminished biological activity relative to their neutral forms, THCA and CBDA are commonly decarboxylated via heating or combustion during the process of smoking (for either raw flower or various types of extracts) or prior to ingestion of formulated edible products.
Figure 1: Primary cannabinoids of interest in medical cannabis.
Liquid chromatography with multiple wavelength or continuous array ultraviolet-visible (UV-vis) detection is a robust, capable, and economical choice for routine cannabinoid analysis in a variety of matrices. A standard consortium of 5–9 cannabinoids typically detected and quantified in cannabis flower and related products is easily characterized via retention time and spectral matching for peaks of interest with a binary solvent gradient method of 5–40 min for HPLC and -5–10 min for UHPLC, with sensitivities approaching 0.05 weight percent for the major cannabinoids. Stock solutions were prepared in methanol for calibration curves. Standards were mixed at different concentrations to create calibration curves with linear ranges that would reflect expected marijuana flower and extract concentrations for the analytes. Table I details the preparation of the calibration solution for cannabis flower samples and extract samples. Both sample types, extracts and flower samples, are able to utilize the same curve.
Gas chromatography (GC) has historically been the default analytical method of choice for cannabinoid determination due to its widespread availability and low cost. Most cannabis analytical chemists now prefer HPLC and UHPLC due to an increased desire to report the sum of the acid and neutral forms of the major cannabinoids during potency quantitation. The results obtained showed excellent accuracy between the two systems and demonstrate the ability of the LC system to generate the same accurate result as more expensive and complicated systems. Please visit www.LQA.com/cannabis to download a complete copy of this application note, and learn how Quantum Analytics can help make cannabis analysis a reality for your laboratory with low cost, easy-to-use HPLC systems coupled with simple lease and financing options.
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