A Certificate of Analysis records what a specific lot was measured to contain, by a stated method, on a stated date. Most of the difficulty in reading one comes from suppliers presenting a document that looks like this but is not tied to the material you were sent.
The four fields that carry the weight
1. The lot number
This is the load-bearing field. It is the only thing connecting the certificate to your vial. A purity figure with no lot number attached describes some batch, at some point, at that supplier — and there is no way to establish whether it is yours. Check that the number on the certificate matches the number printed on the vial label and on the carton.
2. The analytical method
Different methods answer different questions. A purity figure is only interpretable if you know what produced it. A certificate that reports a number without naming the method has told you less than it appears to.
3. The result
Note the difference between a specification and a result. A specification is the acceptance criterion the material had to meet — for example ≥ 99% by HPLC. A result is what this lot actually measured. Catalogues frequently print the specification and let it read as the result.
4. The date of analysis
This anchors the certificate in time. Without it you cannot tell whether the document describes recent material or was issued years ago and has been reused since.
The failure mode to watch for
The common pattern is not a forged certificate. It is a real certificate for a real batch, reused across every later batch. Everything on the page is true; it just does not describe what shipped to you. The tell is always the same — a purity figure presented at the catalogue level rather than attached to a lot.
What a certificate cannot tell you
It records a lot at the point of release. It says nothing about how that material was handled afterwards, which is why storage conditions matter at your end — see storage and handling. A certificate is evidence about origin, not a guarantee about the present state of a vial that has been sitting somewhere warm.
Every lot released here publishes its own certificate. You can read any of them, before ordering, in the COA library.
Common questions
- What is a Certificate of Analysis?
- A document recording what a specific lot was measured to contain: the analytical method used, the purity result, and the date of analysis. It describes one lot on one date — not a product line in general.
- What should a COA actually state?
- A lot number that matches the vial, the analytical method, the measured purity result, and the date of analysis. If any of those is missing, the document cannot be tied to the material in front of you.
- Why does the lot number matter so much?
- It is the only thing connecting the certificate to your vial. A purity figure with no lot number attached describes some batch at some point. It may or may not be the one you received.
- What does a COA not tell you?
- How the material was handled after release. A certificate records the state of a lot when it was analysed; storage and handling afterwards are outside its scope, which is why storage conditions matter at your end.