How to Read a Peptide Certificate of Analysis (COA)

A Certificate of Analysis (COA) is the single most important document a research-peptide vendor can provide. But a PDF on its own proves nothing — what matters is whether each test is present, current, and matched to the exact vial in your hand.

Start with batch matching. The batch or lot number printed on your vial must match the batch number on the COA. If they don't match, the results describe a different production run and tell you nothing about your material.

Next, look for two distinct analytical methods. HPLC (high-performance liquid chromatography) measures purity — how much of the sample is the target compound versus impurities. Mass spectrometry confirms identity — that the molecule is actually the peptide you ordered, not an unrelated compound of similar weight. A strong COA shows both.

For anything intended for injection in a research model, also check for an endotoxin (LAL) result and a sterility statement. Finally, confirm the testing lab is a recognized third party — names like Janoshik, MZ Biolabs, or Colmaric — and that the test date is recent, ideally within the last 12 months.

At VeriPeptides, every batch ships with a third-party COA you can pull up by entering the batch number on our Verify page. No login, no email gate — just the data.