A plain-English guide to reading a research-peptide certificate of analysis — HPLC purity, mass-spec identity, lot numbers, and what actually matters.
A certificate of analysis (COA) is the independent lab report that documents what's actually in a research vial. A real one is tied to a specific lot number — the same number printed on the vial in your hand.
High-performance liquid chromatography separates a sample into its components. The purity figure (e.g. >99%) is the area of the target peak versus everything else. Look for the chromatogram itself, not just a number typed on a page.
Mass spectrometry confirms the compound is what the label says by measuring its molecular mass. Identity + purity together are the two questions a COA should answer.
The COA's lot number must match the vial. If a supplier can't show a lot-matched COA, you can't verify what you received.