Certificate of Analysis (COA).

A lab document reporting a batch's identity and purity tests.

A Certificate of Analysis reports analytical test results for a specific manufactured batch, typically covering identity, usually confirmed by mass spectrometry, and purity, usually estimated by HPLC, sometimes alongside water content, peptide content, and appearance. Read properly, a COA answers a narrow chemistry question: is the molecule in this batch the one named on the label, and how much of the material is that molecule rather than something else. That is genuinely useful information, and its absence is a meaningful warning sign. The limits are equally important. A COA describes one batch, so it says nothing about the vial you actually received unless the batch numbers match. It is only as trustworthy as the laboratory that produced it, and a document supplied by the seller with no independent testing house named carries little weight. Standard purity and identity testing does not address sterility or endotoxin unless those tests are specifically listed. And most fundamentally, a COA is a chemistry document: it cannot establish that a compound is safe in humans, effective for anything, or legal to use. The misunderstanding worth correcting is treating a COA as a quality seal or a safety endorsement rather than as a batch test result with a defined and limited scope.