# Residual solvents

> A residual solvents test measures leftover solvents such as butane, propane, ethanol or hexane in an extract, usually by headspace GC, against safety limits.

- Canonical: https://genetixbay.com/knowledge/glossary/residual-solvents.html
- Also written: residual solvent test, residual solvents test, solvent residue, residual solvent panel, RS test
- Glossary category: Lab testing · Evidence: Established
- Status: Draft: awaiting expert review · Updated: 2026-10-31
- Licence: CC BY-SA 4.0 (https://creativecommons.org/licenses/by-sa/4.0/), attribute "GenetixBay cannabis glossary"

Residual solvents testing checks how much of the solvents used in, or contaminating, an extract remain in the finished product. The standard method is headspace [gas chromatography](https://genetixbay.com/knowledge/glossary/gas-chromatography.md): the sample is warmed in a sealed vial and the vapour above it is analysed, typically with FID or MS detection. Panels cover common extraction solvents (butane, propane, ethanol, hexane, heptane, acetone, isopropanol) and sometimes contaminants such as benzene.

## In practice

This test applies mainly to solvent-based concentrates, though some markets require it for any extract. A [COA](https://genetixbay.com/knowledge/glossary/coa.md) lists each solvent in ppm (µg/g) against a limit; limits vary widely by solvent and jurisdiction, with lower-toxicity solvents generally allowed at higher levels. [Solventless](https://genetixbay.com/knowledge/glossary/solventless.md) products such as [rosin](https://genetixbay.com/knowledge/glossary/rosin.md) and [ice water hash](https://genetixbay.com/knowledge/glossary/bubble-hash.md) should read [ND](https://genetixbay.com/knowledge/glossary/non-detect.md), though some markets still test them. GenetixBay doesn't cover extraction methods; this entry defines the test only.

## Units and formula

ppm = µg/g. Results are compared with solvent-specific action limits.

## Don't confuse with

- **Terpene test**: also GC, but measuring aroma compounds rather than solvents.
- **Solventless**: describes a production method; the test confirms the outcome.

## Related terms

[Gas chromatography](https://genetixbay.com/knowledge/glossary/gas-chromatography.md), [Solvent-based extract](https://genetixbay.com/knowledge/glossary/solvent-based-extract.md), [Concentrate](https://genetixbay.com/knowledge/glossary/concentrate.md), [COA](https://genetixbay.com/knowledge/glossary/coa.md), [LOD](https://genetixbay.com/knowledge/glossary/lod.md)