Residual solvents

Residual solvents are traces of the chemicals used during extraction or processing that remain in a finished extract or product.

Ethanol, butane, propane, hexane, heptane and isopropanol are among the solvents used to pull cannabinoids from hemp or to clean up an extract, and each must be removed by evaporation or vacuum before the material is used. Carbon dioxide extraction leaves no solvent residue, though solvents may still be introduced in later refining. Permitted limits differ by solvent according to its toxicity.

On a certificate of analysis the section lists each solvent the laboratory tests for, usually by gas chromatography, with a measured value in parts per million, the reporting limit and an action limit. A pass means each solvent was below its limit; a solvent that was never used will simply read below the reporting limit. Some laboratories omit the test for products made by carbon dioxide extraction, so its absence is not always a red flag but is worth asking about.