reading area percent threads from 2024 and half of it aged badly
reading area percent threads from 2024 and half of it aged badly. I have gone back and forth on this for months. 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. Area percent is the peak area of…
Why the same vial can honestly produce three different numbers.
Purity by area percent is relative to what the detector saw on one gradient at one wavelength. Net peptide content subtracts counterion, water and residual solvent. Mass of peptide per vial is net content times fill weight, and fill weight has its own tolerance.
So a document reading 99% purity, 6% acetate and 4% water is describing a vial that is about 90% peptide by mass, and every one of those numbers is honest. The mistake is treating the headline figure as the answer to "how much peptide did I get".
Does the lot on the vial match the lot on the page?
Yes — and the reason to ask for the whole page is that the interesting parts are the ones people crop out to fit a screenshot.
area% is not mass%, and the difference is the whole game
net peptide content and purity are two different numbers on the same vial
Yes. The structure of the document matters at least as much as the number printed on it.