Tag Archives: supercritical co2

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BEST Extractions

Busting the Myth: Examining CO2 versus Butane Extraction

By John A. Mackay, Ph. D.
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The basis of anecdotal controversy continues about the use of hydrocarbons versus carbon dioxide. It is important to note that hydrocarbons span a range of phases on the planet earth.

It is important to eliminate the cost of the instruments and the cost of the facilities from this comparison to keep the discussion on specifically the extraction principles.

Source: (https://en.wikipedia.org/wiki/Butane#Isomers)
Source: (https://en.wikipedia.org/wiki/Butane#Isomers)

Butane is a gaseous hydrocarbon. As you add more carbons to hydrocarbons, they move from gaseous to liquid.

It is also important to note that the same is true of carbon dioxide in its natural form on the earth’s atmosphere, it is a gas. It is nonflammable and used in fire extinguishers.

At typical conditions, carbon dioxide in the supercritical range is similar to hexane (C6H14) and ethyl acetate in its solubility characteristics. Propane (C3H8) and butane (C4H10) are gases at normal atmospheric conditions. Both must be manipulated for the extraction of CBDA and CBD. For example, both CO2 and C4H10 must be placed under pressure and then passed through the material to extract the lipophilic terpenes and cannabinoids.

For this short discussion, let’s remove the concern about the different volatilities of the compounds. Hydrocarbons with a spark will be significantly more powerful of an explosion than carbon dioxide (note it could be used to put out the butane fire). The hydrocarbons can be in more configurations and therefore the getting the correct form initially is critical. For example, butane can have all the carbons in a row like a train, or branched like a tree. Those are very different and have different characteristics too. Getting pharmaceutical grade butane is essential to ensure safety. The concern that people have expressed with butane is what is in the other 0.1% for 99.9%. Checking for residual butane is less of a concern than the polyaromatic hydrocarbons in the untested cylinder. Furthermore, in the wrong hands it can be more volatile.

Source: (https://en.wikipedia.org/wiki/Carbon_dioxide)
Source: (https://en.wikipedia.org/wiki/Carbon_dioxide)

The critical premise that needs to be considered is the final formulation. Is one solvent significantly more applicable than the other? No. They have different characteristics.

Propane is a common solvent in the spices, flavors and fragrances industry. For example, the extraction of lipids and oils from vegetables and the fatty oils from seeds, it would be an advantage to have a solvent that is totally miscible, i.e. will be totally soluble in a fluid. This is similar to the idea of sugar in hot water versus in water in ice. If an example of cardamom were used comparing CO2 and propane (which is similar to butane), the pressure needed for CO2 would be 100 bar, while propane would be only 20 bar. However the increasing the pressure of the propane from 20 to 50 bar at a constant 25 C, also increases the chlorophyll from 3.4 g/g oil to 10.8 g/g oil. Meanwhile with the more finely tunable CO2 from 80 to 100 to 200 the amount of chlorophyll is negligible (0.36 g/g oil) but at 300 bar it dramatically increases to 4.53 g/g oil.

Additionally the CO2 is a better extraction for the terpenes in the cardamom. The beta-pinine, Cineole, linalool, alpha-terpinol and bornelole. The increase in the propane pressure will allow us to increase the yield of the CO2 (Illes, V, et. al. Proceedings of the Fifth Meeting of Supercritical Fluids, Nice, France, Tome 2, 555-560).

This example is the same with the butane and cannabis. Butane is a stronger solvent and if left too long will continue to pull out more and more polar compounds like chlorophyll. With the fine-tuning of CO2, you can eliminate or you can pull out the chlorophyll if you choose the wrong conditions.

So fast extractions are possible with butane but little control of all the material, while CO2 can be tunable and therefore is able to collect all of the same material, just through a segmented process.

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BEST Extractions

Defining BEST Extraction

By John A. Mackay, Ph. D.
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Over the next few months, I would like to walk through a series of articles to cover the number of ways to extract potentially pharmaceutically active compounds from cannabis plants. However, in the first article I would like to review concerns being addressed in state regulations: contamination in concentrates with pesticides, mycotoxins, and residual solvents. The next article will cover the most common extraction with two different modes: CO2 versus hydrocarbons.

Currently, there is a lot of focus on the cannabis strain of hemp. This is defined as having less than 0.3% of THC, (the psychoactive compound). To be clear, the science of extraction is eons old, but the current revitalization is due to new scientific inquiry regarding the applications of the cannabis plant.

I am often asked, “What is the ‘best’ extraction for a natural product?” The BEST extraction? The key to this answer is that you must assume unintended consequences until you can prove that they are at least minimized compared to the intended consequences.

I have a suggestion for you to consider and I look forward to your response to it. I also assume the right to adapt and revise it.

Botanical integrity from seed to shelf

Efficacy of the process beyond efficiency, economics, effectiveness

Safety of people and product

Testing for confirmation at each step of process

The hemp industry has changed significantly over the past few years. Just casually flipping through the channels on television, reading a newspaper or magazine, (on any topic – news, business, sports, food and science) and there is some facet of hemp’s value being examined. The reduction of traditional pulmonary intake (smoking) in the legal marketplace can be tracked by sales of these products in the states where it is legal. The balance of ingestion is drastically tipping toward what might still be considered smoking with vaporizer products as well as toward edible consumables. The ingredients in these products come not from just adding the plant to the formulation, but rather a concentrated mixture. This is the difference between adding a raw vanilla and a teaspoon of vanilla extract. The compound getting the most coverage is cannabidiol (CBD), which is the compound derived from cannabidiolic acid (CBDA). The effects of the other compounds in the plant are being studied as well.

Unintended consequences from the concentration – extraction – are something we need to consider seriously as consumers. The labeled use of “natural” is one that is critical, but can be totally nullified by the unintended contamination in the extraction workflow. Years of making sure the hemp adheres to strict growing environment can be destroyed in seconds with the addition of polycyclic aromatic hydrocarbons (PAH’s) by the use of solvent that has these toxic chemicals in them. These come not through intended consequences, but not knowing the stabilizers and other additives in material being added to these previously pure plants.

What if I pour sour milk on a natural granola for breakfast? What if I use water with high lead or contaminated water to pour over natural coffee grind? Not a great way to start the day, but it is no different than using the most premium hemp and unknowingly adding low grade solvents or adding components from cleaning the surfaces of instruments that come in contact with hemp.

Note that, by definition, we are concentrating the material from the hemp plant. From 4,000 grams, we are getting 400 grams of CBDA if it is 10% by weight (and later converted to CBD). That compound is 10 times more concentrated in a solution. What other compounds are now also 10 times or 5 times or 100 times more concentrated? Maybe no “bad” ones, but how do you know that something else is not also in the mixture?

figure1 extract
Figure 1. With each step of concentration of the green balls, so it could be with other components in the mixture.

This is illustrated in the filtering of green balls in Figure 1. As the green balls become a greater and greater percentage of the solution, it is possible that other compounds like pesticides are also increasing in percentage of the extraction solution. The solution is more concentrated and “simpler” versus all of the other things in the original mixture.

The simple answer is in the testing of the components. The labeling of major compounds is only the beginning of what is on the label that you read. Heavy metals? PAH’s? Residual solvents? Pesticides? Molds? And a long list of other material that could come into the process after the plant left its pristine organic farm. Many studies can be read about slip agents in bags, contamination from workers in the workflow, and other sources of inconsistency.

There are a significant number of companies that I have seen that take this very seriously. New companies are being formed that have safety of product at the top of the list of importance. They are building facilities that are sterile and putting standard operating procedures in place that continually test the product along every step to ensure that they are in compliance.

ecxtractionfig2
Figure 2. Science and economics merge when considering all the possible uses of concentrated compounds to final product formulations

Supercritical fluid extraction is GRAS (generally regarded as safe). It is, only as long as the solvent specifications are known, the vendor meets those standards, and the instrument surfaces meet any necessary standards.

Supercritical carbon dioxide is used to clean surfaces of electronics and bones for skin grafts. It is used for the decaffeination of coffee as well as pulling trace amounts of pesticides from soil. It is used to extract antioxidants from krill and the active ingredients from algae as well as oil from core samples deep below the earth. It also extracts the terpenes and CBDA from hemp – as well as possibly anything that has been added to it.

The key take away from this article is to know the BEST extraction.

Botanical integrity from seed to shelf

Efficacy of the process beyond efficiency, economics, effectiveness

Safety of people and product

Testing for confirmation

Taking each of these into consideration will bring the best results for concentrations of hemp products. I hope you can extract the best from your day.