Certificate of analysis (COA)

A certificate of analysis is the document a testing laboratory issues for a specific production lot of a compound. For a research peptide it should state the lot number, the test date, the HPLC purity as a percentage, and a mass spectrometry result confirming identity. Better certificates add the peptide content by weight, residual solvent and counter-ion levels, water content, and, for injectable-grade material, endotoxin and sterility results.

Reading one is mostly a matter of knowing which number answers which question. Purity answers "how much of the peptide material is the right sequence". Identity answers "is the right sequence actually present". Peptide content answers "how much of the powder in the vial is peptide at all", which matters because a vial labelled 5 mg may contain 5 mg of peptide plus salts and water. A certificate for a different lot than the one in hand answers nothing about that vial.

Canada Peptides tests every lot by third-party HPLC and supplies the certificate on request; the lab-testing page describes the process and the COA guide walks through a real example.