Certificate of Analysis (COA)
A Certificate of Analysis (COA) is a lab report that verifies what's actually inside a specific batch of a peptide product (its purity percentage, identity, and often its concentration), issued by a third-party testing lab rather than by the seller itself, whether the product in question is a GHS compound, a bioregulator peptide, or a nootropic peptide. In peptide research, the COA is the single most important piece of documentation a vendor can provide, because peptides sold for research use don't go through the FDA approval process that would otherwise guarantee batch consistency, which means the COA is effectively the only independent evidence that a vial contains what its label claims.
A COA that actually means something is tied to a specific batch or lot number, not a generic document reused across every product a vendor sells. The report should include, at minimum, the purity result (usually expressed as a percentage from HPLC testing), a mass spectrometry result confirming the peptide's identity matches its labeled sequence, and the date the sample was tested. A COA without a batch number attached to it is close to worthless as evidence, since there's no way to confirm it corresponds to the specific vial in hand rather than a different, possibly higher-quality batch tested once and reused in marketing indefinitely.
What a COA does and doesn't guarantee
A COA confirms what a lab found in the specific sample it tested. It does not guarantee every vial from that same production run is identical, and it says nothing about storage conditions, shipping handling, or degradation that may have occurred after testing. Purity and identity are the two things a COA is built to verify; sterility, endotoxin levels, and heavy metal contamination are separate tests that a COA doesn't automatically include unless the report explicitly says so. Buyers comparing vendors should check not just whether a COA exists, but which specific tests it covers and whether the testing lab is independent from the seller rather than an in-house lab with an obvious incentive to report favorable numbers.
The testing method itself matters as much as the result. HPLC-MS testing is the standard combination used to produce a credible COA (HPLC separates and quantifies purity, while mass spectrometry confirms molecular identity), and a COA built on weaker or unspecified testing methods carries less weight even if the purity number looks good. Because COA quality and testing rigor vary so widely across the market, comparing vendors on this specific point is one of the more useful ways to sort a crowded field, and that comparison is covered in more depth in the site's vendor and company rankings rather than here. A COA is also the practical difference between a compound sold under a Research Use Only label with real accountability behind it and one sold with the label alone and nothing to back it up.
Where the COA comes from matters too. A report generated by the vendor's own in-house lab carries an inherent conflict of interest (the same party has every incentive to report a clean result), while a report from an accredited, independent third-party lab has no financial stake in the outcome. Some vendors post COAs directly on the product page for every batch; others provide one only on request, or reuse an old report across multiple production runs without disclosing that it's not batch-specific. None of those practices are illegal, since COAs aren't a regulatory requirement for RUO products, but they're exactly the kind of transparency gap worth checking for before treating any single COA as settled proof of what's in a given vial.