reading certificate of analysis threads from 2024 and half of it aged badly
reading certificate of analysis threads from 2024 and half of it aged badly, and I am aware this is a minority view on this board. UV at 214nm sees the peptide bond and picks up almost everything; at 280nm you are looking at aromatics only. Which wavelength the number came from is part of the number. LC-MS gives you…
The PDF creation date being later than the analysis date is usually a re-issue or a re-export. It is worth one question and it is not evidence of anything on its own.
The four things a certificate must carry, and what each one is for.
Batch identifier ties the document to your vial; without it the document is about somebody else’s material. Date of analysis tells you when the number was true. Method — column, gradient, wavelength — is what makes the figure reproducible rather than asserted. Individual related substances give you the shape of what else is in there.
Everything beyond those four is welcome. Anything missing from them is a question to ask before you order, and in my experience the answer arrives quickly from the suppliers who have a batch record to draw it from.
Not quite. Two labs with different gradients can resolve a close-eluting impurity differently and both be reporting honestly.
Agreed — the itemised related substances table is the difference between a document and a receipt.
Small fix — 214nm, not 280nm. It matters here because the impurity you are asking about barely absorbs at the longer wavelength.
Disagree that a lower number is automatically worse. A conservative claim that survives testing is worth more than an optimistic one that does not.
That is not what the method line says. It names the technique; it does not certify the operator.
Small fix — 214nm, not 280nm.
Disagree on this specific point. Two honest labs can resolve that impurity differently and report different numbers.
HPLC-UV and LC-MS answer different questions
ask for the storage condition the stability statement was written against