Question:Â Are you willing to explore a detailed peer reviewed journal article that has extensively explored the key factors in supercritical extraction using carbon dioxide for the extraction of bioactive material versus anecdotal experiences?
Depending on the your reading speed and absorption rate of information, you will, in 10 minutes, learn applied science from chemistry, physics and mathematics. Or in 2 minutes, be off to the next blog. Stay 5 minutes, you might be surprised how it can apply to your daily work, or how to drop the line at dinner tonight…“I was reviewing some interesting work while looking at an old Journal of Supercritical Fluids and came upon something that pertains to all those CBD articles in the local paper”.
This quick 10 minutes is based on several years of work in Dr. Cor Peters lab that Dr. Perrotin-Brunel studied.  It was published 5 years ago.
Background: Carbon dioxide, when above 31.1 C, and 72.8 atmospheres, reaches a state that has been called “supercriticalâ€.
While rebranding of the word would make this seem less imposing, I will just you assure that, while it is super in my mind, and critical to my daily activities, its origin is not based on that. Best to go to Wiki to learn the real reason.[1]
As the pressure and temperature of CO2 change, so does the solubility of the compounds in the CO2. This can be seen in the following three figures.
First, if we hold the temperature constant and increase the pressure, we note, in this instance that solubility increases. More of the compound is dissolved.
Second, if we hold the pressure constant, but increase the temperature, then we again see a trend for greater solubility of CBD. The question you MUST ask is “SO WHAT??† (that is a little loud with the capitals, but I know what you mean… I think)
Looking at these two figures, you might think that all you have to do is increase the temperature and pressure and flow rate of the CO2 passing by the plant material to maximize the extraction of CBD.
However, this is not taking into account a few other facts I neglected to tell you.
- This was extracted from a specific strain of cannabis plant. Notice all the other compounds, just in these figures. There are many others. A few are shown in figure below.  Also each strain will extract differently based on all of the other components, as well as moisture, particle size, pH, etc.
This adds a bit of complexity doesn’t it?
- How is it possible to collect the material?
Ah… glad you asked. (I love this part).
There is an important fact:  if CBD is partially soluble at a specific temperature and pressure, then it is also partially insoluble at the same pressure and temperature. Or even better, if you want to set conditions to make it most soluble, then you can change the conditions to make it most insoluble.  Let’s use the data to see what the effect would be for this.
So if we were to set up an experiment to test these conditions it would look below.
Which vessel would you believe the most amount of CBD would precipitate?
Another factor that must be considered is the mass transfer of the components from the plant material and the precipitation rate in the collection vessels. Based on these conditions you would be able to extract the material, however the rate of extraction could be enhanced at higher pressure and lower temperatures to reduce the amount of non-value added material such as the waxes.
The other part is an advantage from knowing the solubility of the individual components seen is the ability to have steps on the extraction side. A better way to do this would be to have a very low pressure and temperature to start off to extract the high volatile flavors and fragrances, then increase to gain the neutrals (like CBD) and finally increase again to extract the less soluble polar acids (CBD-Acid).
This can be seen in the following two diagrams. They are dependent up the concentration of the bioactive compounds as well as the amount and type of material.
With the red lines you can see the varying of pressure and the temperature being constant, and the blue line is the flow rate to be able to monitor the removal of the extracted materials delivery to the collection vessel.
So today, if you got this far….you have learned applied science in less than 10 minutes.
If would like me to expand on the details, just put in the comments field or email, as well as what would like to know more about?
[1]Â https://en.wikipedia.org/wiki/Supercritical_fluid
