- Recent events, including legalization of industrial hemp cultivation and processing in the US, have led to a boom of hemp-derived products. Most notable among these are cannabidiol (CBD) oils, tinctures, infusions, edibles, and other consumables.
- Although hemp-derived CBD is technically legal, the Food and Drug Administration (FDA) retains jurisdiction of CBD, actively monitoring products, marketing activities, and unsupported or illegal claims of therapeutic value. Products must adhere the Federal Food, Drug, and Cosmetics Act (FD&C Act) and steer clear of definitions such as dietary supplements or medical products.
- Each state retains the responsibility to draft and enforce testing regulations around CBD and other hemp-derived compounds and products. There exist stipulations around interstate commerce of CBD consumables as well.
Although the legal definitions around CBD products are still taking shape, ultimitately, the responsibility for safety will lay not only with the state but with the consumer. As such, valid results from state-of-testing technologies will provide the best solution to ensure CBD product integrity.
Along with its psychoactive relative THC, the CBD compound is the most abundant cannabinoid found in cannabis, although the balance can tip heavily depending on the source. Hemp is an offshoot of cannabis (both marijuana and hemp derive from Cannabis sativa) and unique characteristics include tough fibrous stalks, a bounty of leaves as opposed to flower, and most importantly, high levels of CBD and very low levels of THC. The legal classification of hemp specifies <0.3% THC by dry weight.
Although CBD derived from legal hemp farming is itself legal, the methods for testing and reporting remain sources of conjecture and concern.
Testing for CBD potency
An initial objective in hemp potency testing may involve assessment to determine not only CBD levels, but to ensure THC levels do not exceed to legal limit of 0.3% THC. This analysis includes testing at the cultivation stage, as cannabis crops can vary significantly in cannabinoid levels and ratios according to the cultivar or breed, and environmental conditions such as grow location, light source, soil conditions, and other factors. Cannabinoid potency testing at downstream processing stages is required to ensure desired levels are maintained to the point of sale.
Rather than focus on how the below potency tests work, we’ll concentrate on what results each test can provide.
High-performance liquid chromatography (HPLC) is a preferred method for potency analysis
Cannabinoids including CBD and THC that partition in the aqueous polar phase following extraction can be readily tested by HPLC. Following sample extraction and filtration to ensure the cannabinoid mix is stable and free from particulates, the sample can be injected into the HPLC, directly or through use of an autosampler. Column separation and compound quantification using cannabinoid internal standards can then be performed. A wide range of HPLC instrument platforms are available to perform quick and/or comprehensive cannabinoid potency analysis.
Specified HPLC systems can be deployed outside of a dedicated testing lab environment, to operate in a mobile lab or remote site such as a grow operation. Turn-key hemp analyzers offer a comprehensive package of instrumentation, software, consumables, and analytical methods, to enable rapid potency testing at the point of cultivation, early processing, and multiple downstream stages.
HPLC systems and all-in-one analyzers are often setup to measure cannabinoid panels using pre-configured and scalable methods. These devices and methods may in certain cases be challenged by overly complex sample backgrounds arising from various food and product sources.
Complex substances such as carbohydrates, fats and lipids, proteins, and other compound classes found in food items require serious consideration when extracting and prepping the sample for HPLC analysis. SPE, liquid-liquid, QuEChERS, and other enrichment techniques may produce extracts which are ripe with information content but overly complex for typical one-dimensional HPLC. In these cases, HPLC inline with MS (LC-MS) can add considerable breadth and depth to compound analysis. LC-MS typically comes with the requirement for designated lab testing facilities and infrastructure, and associated costs.
Methods for potency determination include analysis by gas chromatography (GC)
GC can measure volatile compounds in the gas phase based on chromatographic separation on a solid support or column. GC is useful for hemp analysis as cannabinoids such as CBD may partition in organic solvents and demonstrate elevated volatility due to the given extraction and sample preparation methods. Sample can be injected and ionized by flame ionization, and combined with gas headstage if necessary, prior to column separation. Low abundance compounds are typically amenable for analysis, and quantification is achieved by the use of internal cannabinoid standards.
GC may influence heat-labile cannabinoids, such as the THCA and CBDA – the inactive precursors to THC and CBD – thereby leading to falsely inflated THC and CBD potency measurements. Complex GC and GS-MS (and LC-MS) systems for product analysis typically require controlled lab environments and infrastructure, and although the test data generated can be more comprehensive in these cases, the facilities and infrastructure can come with increased costs.
Emerging potency analysis technologies
Testing technologies have been evolving the suit the growing needs of the cannabis safety and quality assurance areas.
Ultra-high performance liquid chromatography (UHPLC)
This platform offers several advantages over standard HPLC, including higher pressures, shorter column run times, and significantly less mobile phase consumption. The high resolution, high efficiency technique, while ideal for potency testing, may be challenged by lower throughput when processing large sample numbers.
Supercritical Fluid Chromatography (SFC)
This technique has many of the advantages of UHPLC with added benefit of greatly simplified sample preparation requirements. Another strength over and above HPLC in general, is that SFC is compatible with non-polar solutions, making analysis of cannabinoids in lipiphilic matrices - such as those arising from cannabis infused food products - amenable for analysis.
Cannabinoid analysis by FTIR
FTIR allows non-destructive CBD/THC potency determination in minimally processed raw cannabis. The use of a near-infrared module (NIRM) and sample spinner provides a quick and simple method, avoiding extensive sample prep and the use of extraction chemicals. The technique may be well-suited for on-site potency testing of raw cannabis material, with the advantage of subsequent downstream testing using more extensive workflows with the same sample or batch of material.
Compact MS and LC-MS solutions
Platforms which serve as valuable resources in the food industry are beginning to enter the cannabis arena, to serve as remote testing devices for cannabinoid identification, pesticides detection, and residual solvents analysis.
The cannabis industry will benefit from the food industry, namely in the areas of safety testing standards and instrumentation, as consumer preferences shift towards quality over convenience and price.
CBD potency testing summary
- Pretesting at remote sites and/or cannabis harvesting locations may help streamline cultivation and steer clear of potency inconsistencies at the source.
- States with legalized cannabis have legal requirements for standard samples to be sent out to a third-party testing lab to ensure potency, pesticides, terpenoid profiling and other state regulations are met.
- Use of third-party testing labs which adopt GLP standards and comprehensive and transparent reporting measures can ensure the product bears the quality and integrity that consumers value.
- The rigor with which potency testing is performed, the transparency that accompanies test reporting, and integrity of the testing process, together translate to the highest quality and safety for consumer cannabis products.
As legal details unfold, high-quality potency testing for CBD will continue to represent a growing stake in the multi-billion dollar CBD product boom.
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