There are many chromatography-based techniques being used and discussed in the cannabis industry, but one technique that deserves a bit more focus as it moves into the forefront of laboratories is countercurrent chromatography (CCC). CCC is a type of liquid–liquid chromatography that uses a liquid stationary phase held in place by centrifugal force and is used to separate, identify, and quantify the chemical components of a mixture, such as cannabis. Dr. Les Brown, Managing Director of AECS-QuikPrep Ltd., recently spoke to us about the benefits of CCC compared to other methods as well as the work his company has been doing to advance the technique for their clients in the cannabis industry.
Please tell us about countercurrent chromatography (CCC) and how it is being used in the cannabis industry.
Dr. Les Brown: My company has specialized in cannabinoid purifications for more than 10 years by liquid–liquid chromatography (hydrodynamic CCC and hydrostatic CCC, also referred to as centrifugal partition chromatography [CPC]). We have been contracted for several cannabinoid research contracts, with subsequent instrument purchases. We have trained client staff during our instrument installations for cannabinoid purifications, at both research and process scale operations.
The main interests are:
- Removal of tetrahydrocannabinol (THC) to below 0.3% in broad spectrum hemp extracts.
- Removal of state defined contaminants from process scale purifications of THC, cannabidiol (CBD), and so forth.
- Research into alternative biphasic solvents systems that do not use alkanes.
- Identifying and purifying trace medicinal cannabinoids to assist novel human and animal medicine developments.
What advantages does CCC offer compared to other chromatography methods, such as high-performance liquid chromatography (HPLC)?
Brown: There are several advantages, such as:
- No on-column absorption or degradation or infinite retention, with generally 95% to 99%+ mass balance, for mass injected to mass recovered.
- No expensive stationary phase to buy, no column packing facilities required, and no solid phase disposal issues.
- Reduction of solvent use for same mass of product. Reductions can vary, but generally 1/2 to 1/5 of solvent may be used compared to HPLC. Greater savings are achievable if comparing to flash chromatography
- The same instrument can prepare infinitely polar or infinitely nonpolar compounds merely by changing the biphasic solvent choice
What challenges are faced in designing a CCC solvent system for a specific separation, such as medicinal cannabinoids?
Brown: If one understands basic chemistry principles, the implications of solvency, density, surface tension, emulsifying agents to biphasic systems, plus compound and target compound functionality, the Synder polarity triangle, and so on, and can shake solvents in a 10 mL stopper measuring cylinder to define partition coefficient in upper and lower phase, then biphasic solvent choice is extremely intuitive.
It is a shame that nonchemists insist on a “witches brew” approach of set ratios, which has held CCC and CPC back for decades.
We have been developing the use of ionic liquids in CCC and CPC for eight years. Ionic liquids offer amazing alternatives. I believe the future for cannabinoids, monoclonal antibodies (mAbs), proteins, pharmaceuticals, petrochemicals, precious metals, lanthanides, and actinides will ultimately be two solvent ionic liquid based biphasic solvent systems for large scale process. This will ease one of the cost elements in all liquid–liquid chromatography and extraction uses (namely, eluent recycling).