How to Read a Certificate of Analysis (COA)
A practical guide to interpreting a peptide Certificate of Analysis so you can verify what you're actually buying.
Why the COA matters most
A Certificate of Analysis is an independent lab's report on a specific batch of product. It is the single most reliable way to verify that what's on the label matches what's in the vial. If a supplier can't or won't provide one, that's a red flag.
What to look for
Check three things: the purity figure (usually by HPLC, ideally ≥99%), the identity confirmation (typically by mass spectrometry, matching the expected molecular weight), and the batch/lot number — which should match the product you received, not a generic sample.
Bonus signals: a recent test date, the name of an independent lab (not the seller's in-house claim), and a publicly accessible certificate rather than one provided only on request.
Putting it together
A trustworthy COA is batch-specific, from a third party, and confirms both purity and identity. Suppliers that make these easy to find score highest in our rankings — it's the clearest evidence of the quality control that research depends on.
References & Further Reading
- 1.Certificate of Analysis — overview
- 2.HPLC — how purity is measured
- 3.Mass spectrometry — identity confirmation
External links are provided for research reference only and do not constitute an endorsement or medical advice.
Marcus Reed
Lead Researcher & Editor
Marcus leads research and editorial at Top5 Peptides. He and the team evaluate every supplier against the same criteria — independent third-party testing, purity documentation, pricing, and shipping — so the rankings stay consistent and impartial.