A certificate of analysis (CoA) is the document that backs up a purity claim. Here is how to read one without a chemistry degree.
The key fields
Look for the compound name and identity confirmation, the measured purity percentage, the testing method (usually HPLC, sometimes mass spectrometry), and the batch or lot number. That lot number should match the one on your vial.
For laboratory research use only. Not for human or veterinary use.