Significance and Use
5.1 Gas chromatography and flame ionization detection provides a rapid means to identify and quantify cannabinoids in a variety of samples of interest. This test method allows producers of cannabis products to improve and optimize the quality of their products. For example, hemp extractors can use it to determine the efficiency of extraction processes and to verify that products meet regulatory requirements, ensuring safety and quality of products.
5.2 Cannabinoids, such as CBD and THC can be monitored throughout the production process. The determination of Δ9-THC is often required for regulatory purposes and the determination of other THC isomers is often of interest. The United Nations Office on Drugs and Crime provides experimental details and guidance for use of GC to analyze cannabis related samples, including conditions suitable for decarboxylation of cannabinoid acids.
5.3 Post-decarboxylated methodology is used. In decarboxylation, heat is used to liberate carbon dioxide from carboxylic acid cannabinoids, forming their corresponding neutral cannabinoids, for example, THC from THCA. It should be recognized that the hot temperature of the GC injection port itself is capable of effecting at least some decarboxylation (250 °C – ), and many sample types, such as distillates, require no decarboxylation because it would have occurred during material processing. Therefore, some knowledge of sample properties and material processing is useful. Resulting determinations are for the total cannabinoid content of specific isomers, for example, total Δ9-THC. For those samples requiring decarboxylation, the method is validated per Practice through the use of reference materials, spike and recovery of knowns, or through comparison with LC results. For example, carrying out the decarboxylation procedure of a standard containing known amounts of CBDA and CBN should yield the correct amounts of CBD and CBN, where CBN is not significantly changed and the mass of CBD formed from CBDA should be 0.877 × CBDA. The same ratio applies to THC and THCA. For other cannabinoids of interest, the conversion factor is derived from the ratio of formula masses of the neutral to that of its acid. If the observed conversion deviates significantly from expected results, then corrective action is necessary.
5.4 As an aid, users are referred to other methods for determination of individual cannabinoids and their acids, for example, Test Method .
Note 1: Other ASTM standards are in development.
1.1 This test method covers the analysis of cannabinoids in cannabis products by gas chromatography (GC) and flame ionization detection (FID).
1.2 This test method is applicable to cannabis raw materials and resin cannabis products as defined in Guide , including those from hemp. Such material includes: biomass; plant material; flowers; resins; extracts; distillates; recovered solvents; and other intermediate processing material. The applicable concentration range of analysis will vary to some extent depending on the nature of the sample, for instance measurement of delta-9-tetrahydrocannabinol (Δ9-THC) for regulatory purposes in hemp would require calibration to lower concentration levels compared to measurement of CBD in its isolate; however, in most cases, the test method is applicable to the determination of major and minor cannabinoids above about 0.1 mass% in concentration. Dilution of sample solutions is used to adjust concentrations to fall within appropriate calibration curves. Particular emphasis is placed on the determination of Δ9-THC for regulatory compliance purposes and control. This test method can measure any cannabinoid that is eluted and detected from a GC column with sufficient resolution from any interfering compounds. Typical cannabinoids of interest that can be determined by this test method are shown in Table 1. Use of an HPLC technique is recommended if individual measurement of acids, such as THCA, is required.
1.3 The test method does not purport to identify all individual cannabinoids; however, individual users can adapt this test method for specific custom analyses to meet their needs.
1.4 Units—Values stated in SI units are to be regarded as the standard. No other units of measurement are included in this standard.
1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.
1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.