Determining the Quality of High Purity Cannabidiol Isolates

A UPLC-based method for the accurate quantitation of cannabidiol (CBD) in high purity isolates has recently been published by chemists at Waters with assistance from their partners at ProVerde Labs.  As the demand for CBD-containing products soars around the world, determining the composition and purity of CBD isolates is becoming increasingly important for two key reasons. Firstly, to ensure that the product is safe for consumption and, labeled correctly. And, secondly to ensure that manufacturers of these products know exactly how much CBD they are adding to their formulations. This allows them to meet their customers’ needs and, protect against financial loss associated with inadvertently adding too much CBD to a batch. The paper was published in the Journal of Liquid Chromatography & Related Technologies.

To find out more about this method and other related work scientists at Waters are engaged in, we spoke to corresponding author Catharine Layton, Senior Technical Applications Chemist, Waters. 

JR: In simple terms what’s the total test time, accuracy, and reliability of this method? 

CL: Our goal in the development and publication of this method was to provide a simple, validated, “dilute and shoot” method for the assay determination of high purity CBD isolates. The separation, achieved with isocratic chromatography, provides increased efficiency compared to traditional high-performance liquid chromatography (HPLC) methods by utilizing high-throughput, ultra high performance liquid chromatography (UPLC). Using UPLC and a simple sample preparation protocol, assay quantification of a CBD sample, from crystalline isolate to result, can be successfully accomplished with a 1-minute sample preparation followed by a 2-minute runtime.

The ICH Harmonized Tripartite Guideline, “Validation of Analytical Procedures: Text and Methodology Q1(R2)” document defines acceptable methods for determining the accuracy of an assay method. The document states that accuracy can be inferred after method specificity, linearity and precision have been successfully established. Each of these three qualifying validation characteristics was demonstrated in our method validation. For example, the method was proven to be specific for CBD in the presence of other major cannabinoids. Resolution of CBD and close eluting cannabinoids (i.e. critical pairs) was monitored throughout the validation with periodic injections to ensure run-to-run and system-to-system consistency. The linear range, referring back to the “dilute and shoot” sample preparation, was determined to be between 0.8 mg/mL and 1.2 mg/mL, to allow the use of stock certified reference standard solutions at 1.0 mg/mL without further manipulation. Reproducibility of the sample preparation, repeatability of replicate injections, and CBD recovery between different laboratories were successfully achieved to demonstrate repeatability, intermediate precision and reproducibility per validation specifications.

Although not defined by the ICH, reliability is often expressed as the trustworthiness or confidence that a method will provide the true result rather than a result that is inadvertently biased. Reliability can be statistically assessed through standardized proficiency testing across multiple laboratories, or by comparing results obtained using orthogonal methodology within a single laboratory. A proficiency test solution containing CBD as the major component, which is not currently available, rather than a mixture of several components at relatively high concentration, would be most relevant.  As a result, method reliability was demonstrated within our laboratory by comparing assay results obtained by an orthogonal methodology (i.e. different column matrix, mobile phase pH and separation conditions).  Reliability was demonstrated, although not included in the article because the orthogonal methodology produced an assay result within ±2.0% of the result obtained by the primary method.

JR: Will you be looking to get this method included as a standard test method by bodies like ASTM D37 or similar? 

CL: The CBD assay method was developed and validated to fill a need communicated to us by several cannabis testing laboratories. Our goal is to share the parameters so that the method can be employed as needed. Although we do not intend to pursue standardized testing certification, if approached directly by the ASTM Committee D37, or a similar standardization organization, we would gladly assist those organizations in moving this method, or other analytical methods that we have developed, forward.  

JR: As you mention in the paper, HPLC is a very well-established technique for this kind of analysis in the world of pharma. What role can vendors like Waters play in translating knowledge like this from other fields into the cannabis industry? 

CL: Waters has collaborated closely with chemical, environmental, food, pharmaceutical, health sciences, and technology industries to provide innovative tools, analytical system solutions, software and services for many years. Because we have worked closely with these diverse organizations, our scientists, engineers, and researchers have accumulated a breadth of technical knowledge. Solutions developed and successfully applied within one industry may provide similar value when employed by a diverse group of markets. For example, the current rules and regulations surrounding the testing of medicinal cannabis products do not require the same level of regulatory oversight necessary for acceptance of a pharmaceutical by the FDA, but it is not a far-reaching idea to think that someday they in fact could. Taking a proactive approach within the cannabis testing industry by observing the experiences, tools, and techniques utilized in other markets can provide an efficient path forward for success.  

JR: Why was Waters partnership with ProVerde so important for this study? And, why are partnerships like this important in the cannabis testing industry in general? 

CL: The partnership with licensed testing laboratories like ProVerde (Milford, Ma), has provided us with the ability to observe testing of “real world” manufactured CBD isolates. Collaborations with testing laboratories such as this help us recognize the current needs of the testing landscape. Laboratories that participate in partnerships such as this gain access to some of the best scientific and technical minds at Waters to solve technical problems and issues they may encounter. We continue to welcome these collaborations and continually look forward to making new partnerships within this evolving technical landscape.

JR: Are you working on any other cannabis testing-related studies at Waters? 

CL: With our team of experts in the design and manufacture of liquid chromatography and mass spectrometry technologies, we continue to innovate products and solutions that create business advantages in the areas of method development, validation, software and regulatory compliance for thousands of laboratory-dependent organizations. We will continue to share our findings at conferences and trade shows to assist customers in the accomplishment of scientific goals, increases in productivity, and the attainment of high return on scientific investments in research, development, and quality control within this emerging field.

Catharine Layton was speaking to Jack Rudd, Managing Editor of Analytical Cannabis.