How to Read a Certificate of Analysis for Research Peptides

What a Certificate of Analysis actually certifies

A Certificate of Analysis (COA) is a lab report generated by testing a specific batch of material, not the compound in general. Two documents are worth telling apart: a COA verifying this vial's batch, versus a generic spec sheet describing what the compound is supposed to look like. Only the first is evidence about what you actually received.

The fields that matter

• Identity confirmation — usually mass spectrometry, confirming the molecule is structurally what it claims to be rather than a related but different peptide.
• Purity, by HPLC — the percentage of the sample that is the target peptide rather than synthesis by-products or degradation fragments. Research-grade material is typically reported at 98%+, premium material 99%+.
• Batch or lot number — ties the document to a specific production run, not the product line generally. This is what lets a testing lab or the seller trace a question back to an actual batch.
• Test date and testing laboratory — a COA with no named lab, or dated in a way that could not plausibly match the batch, is not verifiable.
• Residual solvents / endotoxin data, where reported — not universal, but present on the more thorough reports.

Red flags

• No lab name, or a lab that does not appear to independently exist.
• No batch number — meaning the document cannot be tied to what you actually received.
• Purity reported with no accompanying chromatogram or method behind it.
• The same COA image reused across unrelated product listings.

What "independent" testing means

Independent means the testing laboratory has no ownership or supply relationship with the seller. A COA generated in-house on the seller's own equipment is not independent, whatever the number on it says. Ask who performed the test before asking what it found.