COA

A meaningful COA names the testing laboratory, identifies the specific batch it applies to, and reports both identity and purity. A document with no batch number cannot be matched to the vial in your hand.

Those four are the whole check, and they are checkable in order. Who ran the test, and are they independent of the seller. Which batch the sample came from, and does that batch number appear on your vial. What identity method was used — mass spectrometry answers whether the right molecule is present. What purity figure is reported, by what method, and against what threshold.

Because research chemicals carry no manufacturing standard, the COA is often the only evidence about a given batch. That is also why a fabricated one is worth so much to a seller.