The choice of ethanol concentration depends on the polarity of the target compound and the characteristics of the plant material. Different concentrations are suited to different extraction goals-there's no single concentration that works for all situations.
1. 90%–100% High-Concentration Ethanol
High-concentration ethanol is mainly used for non-polar extraction, with key details:
Application Scope: Ideal for extracting essential oils, resins, terpenes, and certain fat-soluble cannabinoids.
Key Feature: Almost insoluble in water, so it does not carry away water-soluble components (e.g., sugars, proteins, tannins), resulting in a relatively "clean, oily" extract.
Common Uses: Commonly applied in the extraction of cannabis and aromatic plants.
2. 70%–80% Medium-Concentration Ethanol
This is the most widely used concentration range for plant extraction, with the following characteristics:
Primary Application: Especially suitable for traditional Chinese medicine and functional plant extracts.
Core Advantage: Strikes a good balance between polarity and non-polarity-it dissolves moderately polar components (e.g., flavonoids, alkaloids, tannins, phenols) without completely excluding polar components, and the co-extraction of waxes and gums is relatively controllable.
Practical Significance: Many experienced technicians use this concentration as a baseline for extraction trials.
3. Around 50% Low-Concentration Ethanol
Low-concentration ethanol is focused on extracting highly polar components, with details as follows:
Extraction Target: Suitable for extracting highly polar components such as glycosides, phenolic acids, and some anthocyanins (ideal if you need to retain more water-soluble active substances).
Drawbacks: Leads to more impurities in the extract, and the extract is more prone to spoilage.
4. 30% or Lower Ethanol-Water Solution
At this low concentration, ethanol functions as a co-solvent for water, with key points:
Extraction Purpose: Primarily used for extracting highly polar compounds, such as certain alkaloid salts, tannins, and sugars.
Traditional Application: Often used in traditional herbal extraction methods involving water and alcohol precipitation.
Note: The extract has poor stability and requires immediate post-processing.
Practical Tip for Choosing Ethanol Concentration
If you're unsure which concentration to start with, follow these steps:
Begin with70% ethanol-it delivers relatively balanced results for most plant materials with no major biases.
Adjust the concentration higher or lower based on the actual extract results and test data.
The optimal concentration for different plants usually requires several rounds of small-scale trials to determine.
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