A Certificate of Analysis (CoA) is the primary document that tells you what a research batch actually contains — yet it is often skimmed rather than read. Learning to interpret a Certificate of Analysis section by section is one of the highest-leverage skills for anyone responsible for sourcing or quality review.
Identity: is it what it claims to be?
Start at the top. Identity confirmation — typically by mass spectrometry and/or a characteristic chromatographic retention time — establishes that the material matches the stated compound. A CoA without an identity method is incomplete, no matter how clean the purity number looks.
Purity and impurities
Purity is usually reported as an area-percent from a chromatographic assay (often HPLC-UV). Read it alongside the impurity profile: a single high purity figure means less if the method could not resolve closely related impurities. Look for the assay conditions, not just the headline percentage.
Residual solvents and other tests
Depending on the material, a CoA may report residual solvents, water content, or appearance. Each has a defined acceptance limit; the value only means something when you can see the limit it was measured against.
Lot number and traceability
Finally, confirm the lot number ties the certificate to the specific material in hand. A CoA is batch-specific — a certificate for a different lot is a reference, not a guarantee.
Read the whole document
Treat the CoA as a connected record, not a purity headline. Identity, purity, impurity profile, and lot traceability together tell the real story of a batch.
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