What Is a Certificate of Analysis?

A certificate of analysis records what a laboratory measured in a sample: typically identity, purity, appearance and sometimes water content or endotoxin levels.

It applies to the batch tested and nothing else. A certificate whose batch number does not match the vial in hand describes different material.

Signals of a useful COA

The testing laboratory is named and independent of the seller. The date is recent relative to the batch. Both identity and purity are reported, with the chromatogram or spectrum included rather than a bare summary figure.