How to Read a Peptide Certificate of Analysis (COA)
A COA is only useful if you can read it. Here is what each section of a peptide certificate of analysis actually tells you about identity, purity, and handling.
A Certificate of Analysis (COA) is the primary quality document that ships with a research peptide. It links a specific physical vial to the analytical tests run on that synthesis lot. Reading it well is the difference between trusting a number and understanding it.
Identity: is it the right molecule?
Identity is usually confirmed by mass spectrometry (MS). The measured mass should match the theoretical monoisotopic or average mass of the target sequence within the instrument's tolerance. If a COA reports purity but no identity method, treat the identity as unconfirmed.
Purity: how much of it is the target?
Purity is typically reported by reversed-phase HPLC as an area percentage at a given wavelength (often 214 nm). A 99.2% figure means 99.2% of the integrated peak area, not 99.2% of the mass. Look for the method, column, and gradient so the number is reproducible.
Batch traceability and endotoxin
A useful COA names the batch number, the sampling point, and the test dates, and it should be reproducible from an independent third-party lab. Endotoxin results (pass/fail) matter for any downstream in-vitro work with living systems.
What a COA does not tell you
A COA is a snapshot of a lot at test time. It does not certify storage after shipping, nor does it imply any therapeutic property. All materials referenced here are for laboratory and analytical research only — not for human or veterinary use.
Further reading
- High-performance liquid chromatography — the separation technique behind the purity figure.
- Mass spectrometry — the method used to confirm a molecule's identity.
Research use only - not for human or veterinary use. Nothing here is medical advice.