unpopular opinion: most of what gets said here about water content is guesswork
unpopular opinion: most of what gets said here about water content is guesswork, and I am aware this is a minority view on this board. 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. LC-MS gives…
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.
Careful — "the metadata looks odd" is a reason to ask a question, not a conclusion. Re-issues are ordinary.
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.
Net peptide content is the fraction of the powder that is actually peptide once counterion, water and residual solvent are accounted for.
Adding the bit that always gets missed: the lot on the vial has to match the lot on the page, or none of this applies to your material.
Right, and net peptide content is where the counterion and the water go. Both numbers can be honest and very different.
Area percent or net peptide content? They answer different questions.
That is the catalogue certificate rather than the batch-specific one. Same layout, completely different status.
Right, and net peptide content is where the counterion and the water go.
This is the sentence to take away. The rest of the thread is footnotes to it.
This. Area percent answers "what fraction of what the detector saw was the peak I wanted", and people read it as "how much peptide is in the vial".