Residual solvent - Glossary - peptidetesting.cc

Residual solvents are volatile organic chemicals that remain in tiny amounts after a product has been manufactured, dried, and purified. They include substances such as ethanol, ether, acetic acid, DMF, acetonitrile, DMSO, and NMP, which are used during production but provide no therapeutic benefit and can be toxic.

Residual Solvent Testing on a Certificate of Analysis

Laboratories measure residual solvent concentration using gas chromatography (GC) with headspace sampling and compare the results against safety thresholds defined by ICH Q3C and USP <467>. On a Certificate of Analysis, this measurement is a key safety and purity indicator. Because solvents can increase a product's apparent mass, a high purity claim is incomplete unless solvent residues have been quantified separately. Elevated levels can indicate poor manufacturing practices or incomplete drying.

Class 1 solvents should be avoided, as they are known carcinogens or serious hazards.
Class 2 solvents must be limited to strict daily exposure levels.
Class 3 solvents have lower toxic potential compared to the other two classes.

Distinguishing Residual Solvents From Other Residues

Residual solvents are distinct from residual moisture (or water content), which is measured separately, for example by Karl Fischer titration. They are also different from related substances, which are unwanted variants of the peptide molecule itself rather than external process chemicals. Loss on Drying (LoD), a non-specific weight-loss test, should not be treated as equivalent to a targeted GC residual solvent analysis, because LoD captures total weight change from all sources, not solvent-specific residues.

Residual Solvent Testing on a Certificate of Analysis

Distinguishing Residual Solvents From Other Residues

Sources