Start with identity and batch
First, confirm the document names the material you expect and carries a batch identifier. Then check that the batch on the certificate matches the batch on your vial. A COA only describes the batch it names.
Read the reported results
Next, look at the analytical results. A purity figure typically comes from a chromatographic method such as HPLC, and an identity confirmation typically comes from mass spectrometry. Note which methods were used, since that sets the meaning of each result.
Match and file
Finally, match the certificate to the material in your records and keep the two together. Treat a mismatched or missing batch reference as a reason to pause and query before proceeding.
Frequently asked questions
What’s the first thing to check on a COA?
That the batch on the certificate matches the batch on your material.
What does the purity figure usually come from?
Commonly a chromatographic method such as HPLC; the COA states the method used.