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A More Effective and Efficient Approach to Purer Cannabidiol Production Using Centrifugal Partition Chromatography

By Lauren Pahnke
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Many physicians today treat their patients with cannabidiol (CBD, Figure 1), a cannabinoid found in cannabis. CBD is more efficacious over traditional medications, and unlike delta-9 tetrahydrocannbinol (THC), the main psychoactive compound in cannabis, CBD has no psychoactive effects. Researchers have found CBD to be an effective treatment for conditions such as cancer pain, spasticity in multiple sclerosis, and Dravet Syndrome, a form of epilepsy.

CBD is still considered an unsafe drug under federal law, but to meet the medical demand, 17 states in the US recently passed laws allowing individuals to consume CBD for medical purposes. A recent survey found that half of medicinal CBD users rely on the substance by itself for treatment. As doctors start using CBD to treat more patients, the demand for CBD is only expected to rise, and meeting that demand can pose challenges for manufacturers who are not used to producing such high quantities of CBD. Furthermore, as CBD-based drugs become more popular, the US Food and Drug Administration (FDA) will likely require manufacturers to demonstrate they can produce pure, high-quality products.

cannabidiol
Figure 1. The structure of cannabidiol, one of 400 active compounds found in cannabis.

Most manufacturers use chromatography techniques such as high performance liquid chromatography (HPLC) or flash chromatography to isolate compounds from natural product extracts. While these methods are effective for other applications, they are not, however, ideal for CBD isolate production. Crude cannabis oil contains some 400 potentially active compounds and requires pre-treatment prior to traditional chromatography purification. Both HPLC and flash chromatography also require silica resin, an expensive consumable that must be replaced once it is contaminated due to irreversible absorption of compounds from the cannabis extract. All of these factors limit the production capacity for CBD manufacturers.

Additionally, these chromatography methods use large quantities of solvents to elute natural compounds, which negatively impacts the environment.

A Superior Chromatography Method

Centrifugal partition chromatography (CPC) is an alternative chromatography method that can help commercial CBD manufacturers produce greater quantities of pure CBD more quickly and cleanly, using fewer materials and generating less toxic waste. CPC is a highly scalable CBD production process that is environmentally and economically sustainable.

The mechanics of a CPC run are analogous to the mechanics of a standard elution using a traditional chromatography column. While HPLC, for instance, involves eluting cannabis oil through a resin-packed chromatography column, CPC instead elutes the oil through a series of cells embedded into a stack of rotating disks. These cells contain a liquid stationary phase composed of a commonly used fluid such as water, methanol, or heptane, which is held in place by a centrifugal force. A liquid mobile phase migrates from cell to cell as the stacked disks spin. Compounds with greater affinity to the mobile phase are not retained by the stationary phase and pass through the column faster, whereas compounds with a greater affinity to the stationary phase are retained and pass through the column slower, thereby distributing themselves in separate cells (Figure 2).

Figure 2- CPC
Figure 2. How CPC isolates compounds from complex, natural mixtures. As the column spins, the mobile phase (yellow) moves through each cell in series. The compounds in the mobile phase (A, B, and C) diffuse into the stationary phase (blue) at different rates according to their relative affinities for the two phases.

A chemist can choose a biphasic solvent system that will optimize the separation of a target compound such as CBD to extract relatively pure CBD from a cannabis extract in one step. In one small-scale study, researchers injected five grams of crude cannabis oil low in CBD content into a CPC system and obtained 205 milligrams of over 95% pure CBD in 10 minutes.

Using a liquid stationary phase instead of silica imbues CPC with several time and cost benefits. Because natural products such as raw cannabis extract adhere to silica, traditional chromatography columns must be replaced every few weeks. On the other hand, a chemist can simply rinse out the columns in CPC and reuse them. Also, unlike silica columns, liquid solvents such as heptane used in CPC methods can be distilled with a rotary evaporator and recycled, reducing costs.

Environmental Advantages of CPC

The solvents used in chromatography, such as methanol and acetonitrile, are toxic to both humans and the environment. Many environmentally-conscious companies have attempted to replace these toxic solvents with greener alternatives, but these may come with drawbacks. The standard, toxic solvents are so common because they are integral for optimizing purity. Replacing a solvent with an alternative could, therefore, diminish purity and yield. Consequently, a chemist may need to perform additional steps to achieve the same quality and quantity achievable with a toxic solvent. This produces more waste, offsetting the original intent of using the green solvent.

CPC uses the same solvents as traditional chromatography, but it uses them in smaller quantities. Furthermore, as previously mentioned, these solvents can be reused. Hence, the method is effective, more environmentally-friendly, andeconomically feasible.

CPC’s Value in CBD Production

As manufacturers seek to produce larger quantities of pure CBD to meet the demand of patients and physicians, they will need to integrate CPC into their purification workflows. Since CPC produces a relativelyduct on a larger scale, it is equipped to handle the high-volume needs of a large manufacturer. Additionally, because it extracts more CBD from a given volume of raw cannabis extract, and does not use costly silica or require multiple replacement columns, CPC also makes the process of industrial-scale CBD production economically sustainable. Since it also uses significantly less solvent than traditional chromatography, CPC makes it financially feasible to make the process of producing CBD more environmentally-friendly.

Suggested Reading:

CPC 250: Purification of Cannabidiol from Cannabis sativa

Introduction to Centrifugal Partition Chromatography

Marguerite Arnold

Mainstream Media Picks Up On Cannabis

By Marguerite Arnold
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Marguerite Arnold

The British online newspaper, The Guardian, has just begun to cover cannabis. The regular feature, part of their “society” section, is clearly attempting to cover cannabis a bit more consistently and regularly as the California rec market begins to gain (legal) steam.

The writer now helmed to lead this effort is Alex Halperin, a business journalist in the U.S., who landed the gig apparently on the success of Weedweek – a highly cryptic weekly summary blog of mostly U.S.-based industry events and updates.How the Guardian will cover the industry and related issues will be interesting to follow.

This is also not The Guardian’s first foray into the topic. The media outlet, which got its start in the 1800’s in Northern England and expanded dramatically to reach a global digital audience over the past decade, has covered cannabis legalization on a fairly regular basis for the last four years. This new focus also comes at an interesting time. Apart from events in the U.S., Canada is moving forward with recreational this summer. And in Europe, the medical discussion continues apace. That said, it appears the Guardian is going to focus on the U.S. market, at least initially.

It will be interesting to see if that focus shifts (and if they allow other journalists outside of the U.S. to participate in the expanded coverage). While California might well be the largest state economy in general, the Canadian market is already larger and more developed, being regulated nationally across multiple provinces.

Another Mainstream Media Cannabis Column?

This is hardly news. The Guardian is actually treading on ground established already by most of the big news and business publications – including niche publications, blogs and of course, the trade press.

How the Guardian will cover the industry and related issues will be interesting to follow.

The purpose of the column apparently is to spark an “adult conversation” about cannabis – and how it is “changing modern life.” The initial focus on the U.S. market (and California in particular) may have seemed to make sense to a media outlet looking for outrageous stories. But as everyone knows, the U.S. is only one market – and further one still without federal protection.

However, the Guardian is also now competing with other business and mainstream publications that are already in this space. Main Street, the online business ‘zine helmed by Jim Cramer, created one of the first mainstream specialty cannabis sections almost four years ago with the coincidence of the Colorado rec market. Other notable publications and media outlets have significantly increased their coverage of cannabis as well. CNN has been reporting consistently on cannabis topics like legalization and U.S. federal reform efforts for some time now. Business Insider and Forbes have covered ongoing and growing investments and the financial side of things for several years. The Denver Post has its own entirely cannabis-focused subsidiary, The Cannabist.

And as public companies, in both the U.S. and elsewhere have begun to move through the legal thickets of legalization, business-focussed journals and blogs are even beginning to cover cannabis stocks. Starting with Motley Fool and Seeking Alpha (although again, most of this coverage is of companies outside the United States). Specialty publications are also of course, flourishing online, particularly with the beginning of an advertising market that is also beginning to establish itself, albeit around some still thorny regulatory issues.

In general, although the Guardian has a reputation as critical of the British monarchy, with strong left-leaning tendencies, its coverage of the industry has been fairly mainstream – so far at least.

Will that begin to change? And what will really be tackled and covered? And while the ostensible focus is what is going on in the world of cannabis in California (and presumably other foreign markets) could the Guardian’s ostensible new feature also be geared to drive reform at home? The U.K. has yet to even approach the topic of criminalization.

From The Lab

HPLC Column Selection for Cannabis Chromatographers

By Danielle Mackowsky
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If your laboratory utilizes an HPLC system for cannabinoid and pesticide analysis, it can be a daunting task to select a stationary phase that is both practical and sufficient for the separation at hand. Typically, when developing a new method, an analyst will either evaluate a column they already have in house or seek out a referenced phase/dimension in the literature before exploring other available alternatives.

Tetrahydrocannabinol (THC)
Chemical structure of Tetrahydrocannabinol (THC)

A C18 phase is an excellent first choice for non-polar or slightly polar compounds. If the analyte in question has a minimum ratio of three carbon atoms for every heteroatom, it will be sufficiently retained on this phase. THC and other relative cannabinoids are prime candidates for separation via C18 due to their non-polar nature and structural components.

In addition to a universal C18 phase, alternative selectivity options do exist for laboratories concerned with the analysis of cannabinoid content. Another prevalent column choice features an aromatic or poly-aromatic stationary phase. Compatible with highly aqueous mobile phases, aromatic and poly-aromatic columns primarily rely on hydrophobic and π-π interactions as their main analyte retention mechanisms. Poly-aromatic phases provide enhanced retention and are more hydrophobic when compared to a single phenyl ring structure. While C18 phases are not ideal for resolving structural isomers, poly-aromatic columns are capable of separating these ring-based compounds. Chromatographers with a background in forensic analysis may be very familiar with this type of HPLC column due to its extensive use in drug testing applications.

Chemical structure of chlormequat, a hazardous polar pesticide commonly banned for use in cannabis cultivation
Chemical structure of chlormequat, a hazardous polar pesticide commonly banned for use in cannabis cultivation

Besides cannabinoid content, many cannabis scientists are equally concerned with accurate quantitation of pesticides within a given sample. Many pesticides that have found themselves on regulatory lists in states such as Massachusetts, Washington or Nevada are extremely polar. In order to increase retention of these compounds, and thus improve your overall chromatographic method, it can be extremely advantageous to select a column that allows you to start your gradient at 100% aqueous mobile phase. An aqueous or polar modified C18 column contains an embedded polar group, polar side chain or polar end-capping to allow for separation of polar compounds, while still retaining and resolving non-polar analytes. For laboratories that necessitate the use of only one analytical column, an aqueous C18 phase will allow for separation of monitored pesticides without compromising the quality of cannabinoid data produced.

One must also take into account column length, pore size and particle size when purchasing a column. For the purposes of any cannabis related analysis, a pore size of 100-120Å will suffice. Larger pore columns are typically reserved for large peptides, proteins and polymers. Depending on the sensitivity and resolution needed within your laboratory, particle size can range from 1.8-5um, with the highest sensitivity and resolution coming from the smaller particle size. Core shell technology is also a popular option for laboratories who want to keep the pressure of their HPLC system low, without sacrificing any quality of their resolution. Column lengths of 50 or 100 mm are common for chromatographers who want to achieve sufficient sample separation while keeping their run times relatively short.UCTcolumns

Regardless of the HPLC phase selected, it is very important that a guard cartridge is also used. Guard cartridges are traditionally the same phase and particle size of the HPLC column choice and help to prolong analytical column life. They provide additional sample clean up and are widely recommended by the majority of chromatography experts. Upon reviewing one’s options for HPLC phases and acquiring the necessary guard column, your cannabis laboratory will be ready to get the most out of your HPLC system for your analysis needs.

amandarigdon
The Practical Chemist

Easy Ways to Generate Scientifically Sound Data

By Amanda Rigdon
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amandarigdon

I have been working with the chemical analysis side of the cannabis industry for about six years, and I have seen tremendous scientific growth on the part of cannabis labs over that time. Based on conversations with labs and the presentations and forums held at cannabis analytical conferences, I have seen the cannabis analytical industry move from asking, “how do we do this analysis?” to asking “how do we do this analysis right?” This change of focus represents a milestone in the cannabis industry; it means the industry is growing up. Growing up is not always easy, and that is being reflected now in a new focus on understanding and addressing key issues such as pesticides in cannabis products, and asking important questions about how regulation of cannabis labs will occur.

While sometimes painful, growth is always good. To support this evolution, we are now focusing on the contribution that laboratories make to the safety of the cannabis consumer through the generation of quality data. Much of this focus has been on ensuring scientifically sound data through regulation. But Restek is neither a regulatory nor an accrediting body. Restek is dedicated to helping analytical chemists in all industries and regulatory environments produce scientifically sound data through education, technical support and expert advice regarding instrumentation and supplies. I have the privilege of supporting the cannabis analytical testing industry with this goal in mind, which is why I decided to write a regular column detailing simple ways analytical laboratories can improve the quality of their chromatographic data right now, in ways that are easy to implement and are cost effective.

Anyone with an instrument can perform chromatographic analysis and generate data. Even though results are generated, these results may not be valid. At the cannabis industry’s current state, no burden of proof is placed on the analytical laboratory regarding the validity of its results, and there are few gatekeepers between those results and the consumer who is making decisions based on them. Even though some chromatographic instruments are super fancy and expensive, the fact is that every chromatographic instrument – regardless of whether it costs ten thousand or a million dollars – is designed to spit out a number. It is up to the chemist to ensure that number is valid.

In the first couple of paragraphs of this article, I used terms to describe ‘good’ data like ‘scientifically-sound’ or ‘quality’, but at the end of the day, the definition of ‘good’ data is valid data. If you take the literal meaning, valid data is justifiable, logically correct data. Many of the laboratories I have had the pleasure of working with over the years are genuinely dedicated to the production of valid results, but they also need to minimize costs in order to remain competitive. The good news is that laboratories can generate valid scientific results without breaking the bank.

In each of my future articles, I will focus on one aspect of valid data generation, such as calibration and internal standards, explore it in practical detail and go over how that aspect can be applied to common cannabis analyses. The techniques I will be writing about are applied in many other industries, both regulated and non-regulated, so regardless of where the regulations in your state end up, you can already have a head start on the analytical portion of compliance. That means you have more time to focus on the inevitable paperwork portion of regulatory compliance – lucky you! Stay tuned for my next column on instrument calibration, which is the foundation for producing quality data. I think it will be the start of a really good series and I am looking forward to writing it.