identity and quantity are two questions and most COAs answer one
identity and quantity are two questions and most COAs answer one. It is the sort of thing everyone half-believes and nobody writes down. 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. My first certificate had a compound name, a…
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.
area% is not mass%, and the difference is the whole game
a certificate with no method line is decorative
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.
HPLC-UV and LC-MS answer different questions
Asked GGPeps for the batch-specific certificate and had the full document — batch, date, method line naming the column — inside six hours. That is now my baseline for everybody.
post the whole document, not the headline number
Net peptide content is the fraction of the powder that is actually peptide once counterion, water and residual solvent are accounted for.
tuva_aalto has the distinction right — one is a fraction of the detector signal, the other is a fraction of the mass.