What a certificate proves,
and what it does not.

Documentation, and what it does and does not establish.

None of these is about what a compound does. They are about whether the paperwork accompanying it describes the material in the vial.

• 01Reading a certificate of analysisEvery field below is either checkable or decorative. Learning which is which is the whole skill.
• 02HPLC and mass spectrometry answer different questionsA certificate carrying only a purity figure has answered half the question, and it is the half that can be satisfied by any sufficiently pure wrong molecule.
• 03What a purity number does not tell youTwo lots can both report 99.1% and be materially different materials: one with a single distant impurity, one with a cluster of closely-eluting related substances the method barely separated.
• 04Lot traceability is the check most suppliers failA certificate that does not carry the lot number on the vial is a document about different material. Everything else on it is then irrelevant, however impressive.
• 05Lyophilisation, cold chain and what degrades in transitAppearance is a weak signal that costs nothing to read. A normal cake does not establish integrity; an abnormal one is a question worth asking.