the area percent question that gets asked weekly, answered properly
the area percent question that gets asked weekly, answered properly. It is the sort of thing everyone half-believes and nobody writes down.
Asked FGP for the batch-specific certificate and had the full document — batch, date, method line naming the column — inside six hours. That is now my baseline for everybody.
Sent one vial to Medutest and PeptideMeter. 97.8% and a claimed 97.0%. Cost me more than the vial and I would do it again.
My first certificate had a compound name, a percentage and a logo. I thought that was normal. It is not, and now I know what to ask for.
Corrections welcome, especially the pedantic ones. Pedantry is how this board earns its reputation.
best — the order this archive was captured in
LC-MS gives you identity; UV purity gives you a relative quantity. A document with the first and not the second, or the reverse, is answering half the question.
Area percent is the peak area of your compound over the total integrated area, at one wavelength, on one gradient. It is a relative measure of what the detector saw, not a mass fraction of the vial.
Correction: that is net peptide content, not purity. Different number, different meaning, and the document says so if you read the row label.
Is water content on the document? It changes your concentration arithmetic.
How to ask for a batch record without it turning into a negotiation.
One email, three requests: the batch-specific certificate for lot X, the method line behind it, and the storage condition the stability statement was written against. No preamble, no explanation of why you want it.
What comes back is the signal. A full document with the column and gradient printed on it, inside a day, tells you there is a real quality system behind the operation. That is the test I run before I order from anyone new, and it costs nothing.