Science

Solvent Polarity in Cannabis Extraction

Heather Ritchie
Written by Heather Ritchie

Cannabis extraction is about understanding how cannabinoids and other compounds interact with each other.Many extraction methods use solvents that are either chemical or organic to process concentrates.

Solvent Extracts

Common solvents used for extraction are propane, supercritical CO2, ethanol, and butane. These methods work by “dissolving the trichome heads in the liquid solvent which is separated from the plant material and evaporated off in an oven or desiccator and vacuum pump.” The evaporation process ensures that the extract is as pure as possible and that there is minimal solvent residual.

Polarity describes the electrical charge it carries. Compounds that share elections equally are non-polar,and those that share unequally are polar. The polarity is an integral part of extracting the undesirable compounds and material. The terpenes and cannabinoids in cannabis are essentially oils. Oil is non-polar while water is polar and the two repel each other. These two fluids don’t mix because of their different polarity.

Solvents fall into one of two categories:polar or non-polar. Non-polar solvents, like propane and butane, dissolve the non-polar compounds like lipids, oils, and waxes comprisingthe trichome heads. Polar solvents, like ethanol extract polarcompounds. Water insolublemolecules, like chlorophyll a and chlorophyll b,are naturally soluble in alcohols like ethanol.

Positives and Negatives of Some Popular Solvents

Many prefer non-polar solvents since the cannabinoids dissolve into them and there are a variety to choose from.Also, they don’t extract the water-soluble compounds.

One mid-level polarity solvent is isopropanol.It’s inexpensive and easily obtained. Usually, its used in a wash along with other non-polar solvents or as a secondary solvent. The yields are low,but it’s a relatively safe process.  Low concentrations of residual isopropanol can cause gastric disturbances, while higher concentrations can be lethal.

Supercritical CO2 isanother popular extraction solvent. It’s typically considered to be non-polar; however, when pressures and temperatures are increased, it becomes more polar. Thus, this solvent offers polarity tunability.  It’s also non-explosive. The equipment required for this method is expensive,and training is required to operate it safely.

Commonly used for making hash, n-butaneisnon-polar and great at capturing terpenes and cannabinoids. It’s usually odorized so you can tell if there is a leak,but if you’re making hash from it, you need to find a source that’s not odorized.

Hexane

Hexane, another non-polar is often used for food products and pharmaceuticals. Its qualities are similar to butane,but it’s more expensive and harder to get. It will explode or ignite easily in gas form, so safety precautions are crucial when using it.

Ether is often used for pharmaceutical production,and one reason is that it dissipates at room temperature. It is a non-polar solvent and tremendously dangerous to use. If you can obtain it, it can automatically ignite at lower temperatures than other solutions. Only trained lab scientists in a professional setting should use this solvent.

Ethanol extraction is for those that want the efficiency of butane and safety of supercritical CO2. This solvent is different from the others listed as its polar.The FDAgenerally views food-grade ethanol as safe for human consumption,andit’s often used as an additive and food preservative.

Regardless of the chosen solvent extraction, there are several important factors to figure in. It should be safe, cost-effective, and provide a quality extract.

About the author

Heather Ritchie

Heather Ritchie

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