A document issued by an analytical laboratory verifying a peptide product’s identity, purity, molecular weight, and other quality parameters. A COA typically includes HPLC purity data, mass spectrometry confirmation of molecular identity, and sometimes endotoxin or sterility testing results.

In the pharmaceutical world, COAs are routine and regulated. In the research chemical market, their reliability varies. A COA from an independent third-party lab carries more weight than one from the vendor’s own facility. Some vendors provide COAs for specific lot numbers; others provide generic documents. The presence and quality of COA documentation is one of the few objective quality signals available to researchers working with non-pharmaceutical peptide sources.