A Certificate of Analysis (COA) is the single most useful document a research-materials supplier can give you. For every batch of a chemical sequence, it should report three things plainly: the identity test and method used to confirm it, the measured purity, and the laboratory that ran the analysis.
Identity is usually confirmed by HPLC paired with mass spectrometry. Purity is reported as a percentage from the same chromatographic run. Lab attribution matters because an independent, named laboratory is far more meaningful than an unattributed in-house number.
At Defiance International every batch ships with a COA you can verify against the vial's QR code. These materials are supplied for laboratory research use only.