area percent — 13 things I got wrong before I got it right
area percent — 13 things I got wrong before I got it right — a position I have arrived at slowly and would like tested. 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. Asked BCH for the batch-specific…
ask for the storage condition the stability statement was written against
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.
Not quite. Two labs with different gradients can resolve a close-eluting impurity differently and both be reporting honestly.
water content is on there and everyone skips it
Reminder: a question about a document is not an accusation about a supplier, and posts that blur the two get retitled.
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HPLC-UV and LC-MS answer different questions
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.
Small fix — 214nm, not 280nm. It matters here because the impurity you are asking about barely absorbs at the longer wavelength.
Are the related substances itemised or is it a single total?
Spent four months confusing area% and mass% in every post I made here. One explainer thread and it clicked permanently.
Agreed on asking for the storage condition. It is one line and it changes how you read the entire stability claim.