[Discussion] the area percent advice in here is 2 years out of date
the area percent advice in here is 2 years out of date, which sounds obvious until you try to state the evidence for it. Since the title puts numbers in the shop window: 2 years. UV at 214nm sees the peptide bond and picks up almost everything; at 280nm you are looking at aromatics only. Which wavelength the number…
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.
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 lot on the vial has to match the lot on the page
Are the related substances itemised or is it a single total?
Small fix — 214nm, not 280nm. It matters here because the impurity you are asking about barely absorbs at the longer wavelength.
Water content 3.8%, acetate 6.2%, purity 99%, net peptide about 90% of label weight. All four numbers honest, and I had to read it twice.
post the whole document, not the headline number
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.
identity and quantity are two questions and most documents answer one
Disagree that a lower number is automatically worse. A conservative claim that survives testing is worth more than an optimistic one that does not.
Right, and net peptide content is where the counterion and the water go. Both numbers can be honest and very different.
identity and quantity are two questions and most documents answer one
reflux_report has the distinction right — one is a fraction of the detector signal, the other is a fraction of the mass.
reflux_report has the distinction right — one is a fraction of the detector signal, the other is a fraction of the mass.
This is the sentence to take away. The rest of the thread is footnotes to it.
a total of 0.4% tells you less than four named impurities adding to 0.6%