In short: The solvent line is the most overlooked item on a specification, and it changes what you are buying. Two “10:1 extracts” produced with different solvents are different products — different compound profiles, solubility, taste and colour, even though the ratio on the label looks identical. Three checks close the gap: the solvent must be stated explicitly (water, or the ethanol ratio), residual solvent compliance must be declared against a named standard, and the solubility grade must match your dosage form. Everything else is price.
The three solvent families you will be quoted
| Solvent | Extracts well | Residue consideration | Typical use |
|---|---|---|---|
| Water | Water-soluble actives — polysaccharides, many polyphenols, and high-solubility powders | Lowest residue concern; no organic solvent declaration in most cases | Instant powders, beverage and stick-pack applications, high water-solubility grades |
| Ethanol / water–ethanol blends | Certain phenolic and lipophilic compounds that water extracts poorly | Residues must comply with limits — commonly declared against a pharmacopoeial standard such as Eur. Ph. 2.4.24 or ICH Q3C | Where a marker requires an alcohol-compatible extraction |
| Other solvents (e.g. glycerin; hexane in specific processes) | Specialised actives and select lipophilic fractions | Residue compliance for food use must be verified case by case | Only where the target compound cannot be reached otherwise |
Why two identical ratios are not the same product
A ratio (10:1, 4:1) describes a botanical-to-extract relationship, not a chemical profile. Solvent selection decides which compounds are extracted, how the powder behaves in water, and how it tastes and looks. Buyers who compare only ratio and price routinely end up with a material that will not disperse in their application — or that carries an undeclared residual-solvent question in a regulated market.
What to check on the COA
| Check | What good wording looks like | Red flag |
|---|---|---|
| Solvent stated explicitly | “Extraction solvent: Water” or “Water / ethanol (state the ratio)” | No solvent line, or the vague “food-grade solvent” |
| Residual solvent declaration | Numeric limits, or “meets Eur. Ph. 2.4.24” / ICH Q3C with the class named | The words “solvent-free” used in place of a measured declaration |
| Solubility statement | Water solubility percentage or a solubility grade matching your application | Solubility unstated while the product is sold for a beverage application |
| Consistency between spec and COA | The solvent on the COA matches the agreed specification | Specification says water; COA shows an ethanol blend |
Match the solvent grade to your dosage form
| Your application | Grade to specify | Reason |
|---|---|---|
| Instant powder, stick pack, beverage | Water-extracted, high water solubility | Disperses without a carrier or a dispersing aid |
| Hard capsule or tablet | Either solvent family, with particle size and flow specified | Solubility matters less than flow and blend uniformity |
| Marker-driven claim requiring an alcohol-compatible extraction | Water–ethanol blend with declared residue limits | The target compound cannot be reached in water alone |
| Organic-certified finished product | Solvent permitted under the relevant organic programme | Organic status constrains the permitted extraction media |
Two commercial consequences buyers underestimate
- Solubility drives your formulation cost. A water-soluble grade can remove a carrier or a milling step from your process; an incompatible grade adds one. Compare landed cost, not price per kilogram.
- Residual solvent is a release criterion, not a marketing phrase. Declarations must reference a standard and be measured. In regulated markets, “solvent-free” without a declaration invites a documentation gap your buyer’s QA team will find.
FAQ
Is a water extract less potent than an ethanol extract?
It is a different profile, not automatically a weaker one. Solvent selection changes which compounds are extracted. Compare the active marker, its value and the method — not the solvent name alone.
Do I need an organic-certified solvent?
Only if your finished product carries organic certification, in which case the permitted extraction media are defined by that programme. Otherwise standard food-grade solvents with a compliant residue declaration are sufficient.
What does “meets Eur. Ph. 2.4.24” actually mean?
It states that residual solvents were assessed against the European Pharmacopoeia’s residual solvents limits. Ask for the measured values or the class limits applied, not only the compliance statement.
Can a supplier change the solvent without telling me?
Not without breaching the specification. The solvent is part of the agreed specification, so any change requires your written approval and a new specification revision — with a new sample COA.
Why does my powder not dissolve even though it says “water-soluble”?
Solubility is a specification figure, not a binary property; it depends on the marker, the carrier and the particle size. Ask for a water solubility percentage or a solubility grade that matches your application before ordering.
How is residual solvent tested?
Typically by gas chromatography against the limits in ICH Q3C or the equivalent pharmacopoeial standard. Ask which classes apply to your material and what the measured values were on your batch.
Does the solvent affect shelf life?
It can, indirectly. A higher residual moisture requirement and a hygroscopic powder interact, so loss on drying and packaging (food-grade liner, moisture barrier) matter alongside the solvent line.
What should I write in the purchase agreement?
Three lines: the solvent (or ratio), the residue standard it must meet, and the solubility or particle-size grade. Fix all three before production, because they cannot be retrofitted after the batch is made.
LongBio supplies water-extracted, high-solubility grades with full solvent disclosure on every COA — browse the extract range or ask about your application.