Identity and purity are different questions
Mass spectrometry is commonly used to support molecular identity, while chromatographic methods such as HPLC can estimate the proportion of detected material associated with a target peak. Neither result alone proves that a vial is safe for human use.
What a useful COA should make clear
Look for the tested sample identifier, test date, laboratory identity, methods used, raw or interpretable analytical results and whether the sample was supplied directly by the seller or independently obtained.
What a purity percentage does not tell you
A high HPLC percentage does not automatically establish sterility, endotoxin status, correct fill quantity, absence of all contaminants or clinical-grade manufacturing.
Independent verification matters
Testing is stronger when chain of custody is credible and the laboratory is genuinely independent. A vendor-hosted report should be treated as one piece of evidence rather than a guarantee.