How to Read a Certificate of Analysis (COA)
A COA is a lab’s report on what is actually in a vial. Here is what each section means and what questions to ask before trusting one.
What a COA actually certifies
A Certificate of Analysis is a report issued by a testing lab describing what it found when it examined a specific batch, usually identity (is this the compound it claims to be), purity, and sometimes residual solvents or heavy metals.
A COA is only as reliable as the lab that produced it and the batch it was actually tested against. It says nothing by itself about how the product was stored or handled after that test.
The fields worth checking first
Batch or lot number: this should match the number printed on the vial or box you received. A COA for a different batch tells you nothing about the vial in front of you.
Test date and lab name: an independent third-party lab carries more weight than an in-house report, and a report that is years old may predate changes in the supplier’s process.
Method used: identity is commonly checked by mass spectrometry (MS) or HPLC; purity is usually reported as a percentage from HPLC. Reports that only state a percentage with no method listed are harder to verify.
Questions worth asking a supplier
Can you match this COA to the batch number on my order? Is the testing lab independent of the manufacturer? Is a newer COA available if this one is more than a few months old?
A supplier willing to answer these directly, and to link a COA per batch rather than one generic PDF for every order, is giving you more to verify against. Treat that as a starting point for your own due diligence, not a guarantee.
Research use only. This guide is general information, not medical, legal or laboratory-protocol advice. See the full disclaimer for the terms this site operates under.
