reading batch threads from 2024 and half of it aged badly
reading batch threads from 2024 and half of it aged badly. Making the case below, and I expect to lose some of it in the comments. 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. Asked for the storage condition behind the…
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.
identity and quantity are two questions and most documents answer one
Correction: that is net peptide content, not purity. Different number, different meaning, and the document says so if you read the row label.
net peptide content and purity are two different numbers on the same vial
Why the same vial can honestly produce three different numbers.
Purity by area percent is relative to what the detector saw on one gradient at one wavelength. Net peptide content subtracts counterion, water and residual solvent. Mass of peptide per vial is net content times fill weight, and fill weight has its own tolerance.
So a document reading 99% purity, 6% acetate and 4% water is describing a vial that is about 90% peptide by mass, and every one of those numbers is honest. The mistake is treating the headline figure as the answer to "how much peptide did I get".