A COA is only as good as the lab behind it
Buyers frequently accept a supplier-issued Certificate of Analysis without checking whether it is credible. A COA is a claim until verified. The routine below is what separates a documented batch from a marketing document.
Check the basics on the document
A real COA states the batch number, production and test dates, sample quantity, test methods such as HPLC, and the testing entity. Missing any of these is a warning sign, not a formatting preference. Confirm the document covers the actual production batch rather than a generic template.
Confirm the testing entity is independent
Ideally the COA comes from an independent, accredited lab rather than an unaccredited in-house line. Ask for the lab name and accreditation, ISO 17025 where applicable. An unwillingness to name the lab is a stronger signal than the assay number on the page.
Commission a third-party retest for high-value orders
For high-value or high-purity orders, commission an independent lab such as SGS, Eurofins or a local equivalent to retest a sealed sample. A supplier confident in quality will not object. The retest fee paid once protects every future order on that material.
Match the COA to the batch and keep the trail
The COA batch number must match the material you receive; mismatched or reused COAs are a major fraud signal. Store the COA, retest report and communications together so that if a shipment is later disputed, that file is your evidence rather than a recollection.