What is Countercurrent Chromatography?Broadly defined, chromatography is the process a mixture is separated by passing in a solution or a suspension or as a gas through a medium with components are moving at different rates.
This process is crucial for the cannabis industry as it allows several things to happen with products, such as analyzing its composition, the removal of metals from extract, the removal of THC content from hemp, or the isolation of specific cannabinoids to create extracts.
To perform gas chromatography, a sample is dissolved through the use of a solvent and then vaporized to separate the analytes. This process is done by distributing the systems between two phases, a stationary phase, and a mobile phase. Gas chromatography is unique in that it does not use the mobile phase to interact with the analytes.
Liquid chromatography differs from this by relying on interactions with the sample in both the mobile and stationary phases. Due to the variety of forms of liquid chromatography, there are many combinations of interactions between these phases that can be used. However, throughout all liquid chromatography, a liquid is used to carry the sample through the spectrometer for its ability to separate the sample as a solvent.
Countercurrent Chromatography Benefits
Countercurrent chromatography is a form of liquid-liquid chromatography which is unique as both its mobile and its stationary phase are liquid. This allows operators to extrude the column content during the stationary phase, cutting down considerably on the amount of solvent necessary. It also incurs less sample loss as other forms of liquid chromatography suffer from irreversible absorption onto solid supports.
Instead, countercurrent chromatography relies on centrifugal force to hold the liquid stationary phase in place. This method of chromatography comes with several advantages for operators including:
- General reduction to a half or a fifth of solvent required for the same mass of product as compared to HPLC (High-performance liquid chromatography)
- Being able to use the same instrument to prepare infinitely nonpolar or infinitely polar compounds through changing the biphasic solvent in use
- A complete lack of on-column absorption or degradation or infinite retention with 95% to 99% of sample mass recovered
- Not having to purchase an expensive stationary phase, nor dispose of the solid-phase byproduct
- No need for column packing facilities
Issues with Countercurrent Chromatography System
According to Dr. Les Brown, Managing Director of AECS-QuikPrep Ltd., countercurrent chromatography has been held back by those who use too leniently procured mixes for the chromatography process. He has been working with his team to develop the use of ionic liquids in countercurrent chromatography and centrifugal partition chromatography for nearly a decade.
He said: “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.”
While the widespread utilization of ionic liquids will increase the efficiency of countercurrent chromatography more, it is still currently an effective form of chromatography. The fact that no product is burned onto the columns of the machine is a great advantage in terms of mass preservation and maintenance in general.
Countercurrent chromatography capable machines able to handle between 140 to 2000mls are sold by AECS-QuickPrep, ranging from 16,500 to 55,000 euros in price.
When to Implement Countercurrent Chromatography
While it may be cheaper for smaller producers to rely on independent testing to see whether or not their product passes state or federal regulation, larger cultivators benefit from preempting these tests by analyzing their products themselves. Having access to a countercurrent chromatography machine could save several producers with hundreds of acres of hemp from realizing that their product is either contaminated or contains too much THC too late.
Not only would this allow larger producers to realize any issues with their crops early, but they could also use countercurrent chromatography to separate any undesired substances — whether a contaminant in an oil or THC in hemp — from their product. Other forms of chromatography could work to achieve the same thing, but again, countercurrent chromatography runs no risks of burning off parts of the sample on columns, it majorly reduces the need for solvents, and it does not require the transformation of the sample into a gas for treatment.
Although chromatography units are expensive for small-scale producers to consider, for those that can afford them countercurrent chromatography units end up reducing costs by being able to save product they would not have been able to use, by not requiring disposal for the stationary phase, and by requiring less solvent than other forms of chromatography.