genuine question about area percent that I am slightly embarrassed to ask
genuine question about area percent that I am slightly embarrassed to ask. I am not trying to be the "source?" guy. I would just like a source. The four things a certificate must carry, and what each one is for. Batch identifier ties the document to your vial; without it the document is about somebody else’s…
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.
axis labels included, always
HPLC-UV and LC-MS answer different questions
Sent one vial to Medutest and VendorInvestigate. 98.2% and a claimed 97.5%. Cost me more than the vial and I would do it again.
identity and quantity are two questions and most documents answer one
the counterion is part of the mass you paid for
a total of 0.4% tells you less than four named impurities adding to 0.6%
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Small fix — 214nm, not 280nm. It matters here because the impurity you are asking about barely absorbs at the longer wavelength.
Correction: that is net peptide content, not purity. Different number, different meaning, and the document says so if you read the row label.