[Question] certificate of analysis — what am I missing here
Slightly embarrassed to be asking this, but: certificate of analysis — what am I missing here. Spent four months confusing area% and mass% in every post I made here. One explainer thread and it clicked permanently. Water content 3.8%, acetate 6.2%, purity 99%, net peptide about 90% of label weight. All four numbers…
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.
Sent one vial to Janoshik and Medutest. 97.3% and a claimed 97.0%. Cost me more than the vial and I would do it again.
Right, and net peptide content is where the counterion and the water go. Both numbers can be honest and very different.
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.
Yes. The structure of the document matters at least as much as the number printed on it.
Correction: that is net peptide content, not purity. Different number, different meaning, and the document says so if you read the row label.
area% is not mass%, and the difference is the whole game