Certificate of analysis
A certificate of analysis (COA) is a laboratory's report of the tests run on one specific lot of a product, giving each test's method, the limit it was held to where one applies, and the value found.
A COA belongs to a lot, not to a product. It should name the compound, the lot or batch number, the laboratory that did the testing and the date, and for each test the method used and what it found. Purity by HPLC is the most common entry. Identity by mass spectrometry, endotoxin, heavy metals and microbial limits appear on fuller certificates.
Reading one well starts with checking that it covers the material in hand. The lot number on the certificate should match the vial or the order. The laboratory should be named, so that it can be contacted, and some laboratories let anyone look a certificate up by its number. The figures should agree with each other: a stated molecular weight, for example, should match the molecular formula printed beside it.
A COA also has limits. It reports only the tests listed on it, so a purity figure says nothing about identity unless an identity test is shown as well. A certificate issued by the manufacturer is a claim about its own product, while one from an independent laboratory is a check by someone else. And a certificate dated well before a lot was sold describes the material as it was when tested.
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UPDATED OCTOBER 30, 2026 · REVIEWED BY DEL POTTER, PHD