A Certificate of Analysis (CoA) is the single most useful document a supplier can hand you before you trust a compound in your protocol. It's the independent lab's own record of what a specific batch actually contains — not a marketing claim, and not the supplier's own say-so. Knowing how to read one properly turns it from a PDF you skim into a real quality check.
What a CoA certifies
At minimum, a usable CoA identifies the compound, the batch or lot number it applies to, the analytical method used, and the result for each parameter tested. For peptides, the parameter researchers care about most is purity — typically expressed as a percentage by area under the curve from an HPLC trace.
A CoA is only meaningful if it's traceable to the exact unit in front of you. That's what the batch number is for: it links a specific manufacturing run to its specific lab report, so the certificate you're reading actually describes the vial or pen you're holding, not just 'a batch' of the same product line.
Fields worth checking
Beyond the headline purity figure, a well-documented CoA usually breaks out a few supporting details worth a second look before you rely on it:
- Analytical method — RP-HPLC is the standard for peptide purity; mass spectrometry (MS) is often used alongside it to confirm identity.
- Batch or lot number — must match the reference printed on the product label exactly, not just the product name.
- Testing lab — an independent third party is a stronger signal than an in-house-only report.
- Date of analysis — confirms the testing happened against this specific run, not a historical average.
Cross-checking against your order
Once you have a CoA in hand, the quickest sanity check is matching its batch number against the one on your product label. If they don't match, ask the supplier for the correct document before you proceed — a mismatched CoA tells you nothing about what's actually in the vial.
For a faster check without opening a PDF, our batch verification tool looks up the reference printed on your label directly against our current catalog records.