how much of what we believe about area percent actually comes from COA threads
The title is the whole question — how much of what we believe about area percent actually comes from COA threads — but here is why I am asking.
Started keeping a folder of every certificate I have been sent. The ones that itemise impurities are a small group and they are mostly the same suppliers.
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.
The document I was worried about turned out to be a re-issue with a later creation date. Asked, got the original, entirely ordinary.
If somebody has the same thing measured a different way, post it next to mine and we will see whether they agree.
best — the order this archive was captured in
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.
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Does the lot on the vial match the lot on the page?
ask for the storage condition the stability statement was written against
HPLC-UV and LC-MS answer different questions
Reminder: a question about a document is not an accusation about a supplier, and posts that blur the two get retitled.
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 or net peptide content? They answer different questions.
Did you ask for the batch-specific document, or is this the catalogue one?
net peptide content and purity are two different numbers on the same vial
Same view. SSA prints the column and the gradient, which means somebody could actually reproduce the run.
area% is not mass%, and the difference is the whole game
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.
Correcting myself upthread: I said the date was missing and it is on the second page, which I had not scrolled to.
Are the related substances itemised or is it a single total?
Net peptide content is the fraction of the powder that is actually peptide once counterion, water and residual solvent are accounted for. A 99% pure acetate salt can still be about 85% peptide by mass.
Net peptide content is the fraction of the powder that is actually peptide once counterion, water and residual solvent are accounted for.
Disagree on this specific point. Two honest labs can resolve that impurity differently and report different numbers.
I would not read a rounded figure as evasive. Plenty of documents round to one decimal as house style.
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.
That is the catalogue certificate rather than the batch-specific one. Same layout, completely different status.
Asked for the storage condition behind the stability statement. Got it in a sentence. It is a two-line email and almost nobody sends it.
- 1Reminder: a question about a document is not an accusation about a supplier,…7 comments in this branch · started by u/certified_reference
- 2Net peptide content is the fraction of the powder that is actually peptide…7 comments in this branch · started by u/foam_head_fred