[Question] is 99.0% actually fine or am I being sold a rounding error
The claim in the title is exactly the claim I am making: is 99.0% actually fine or am I being sold a rounding error. Nothing implied beyond it. To save the first four comments: 99.0%. Sent one vial to Medutest and Janoshik. 98.4% and a claimed 97.5%. Cost me more than the vial and I would do it again. LC-MS gives you…
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.
I would not read a rounded figure as evasive. Plenty of documents round to one decimal as house style.
the counterion is part of the mass you paid for
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".
My first certificate had a compound name, a percentage and a logo. I thought that was normal. It is not, and now I know what to ask for.
ask for the storage condition the stability statement was written against
That is not what the method line says. It names the technique; it does not certify the operator.
a total of 0.4% tells you less than four named impurities adding to 0.6%
batch number, date of analysis, method, individual impurities — that is the minimum set