#hplc-massspec 2025-07-25

retention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily

monoisotopic and average diverge more the bigger the molecule. say which one you are quoting

ok so how would a truncation sequence show up

shallow gradients hide related substances behind the main peak. a steeper one separates and looks worse, honestly

ok so you need more sample for identity than for purity. plan for that when you post it, ill dig out the number

update from 25 months ago: switched to asking for the chromatogram rather than the number and it changed everything, we shall see
deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant

does ms/ms actually prove identity or just make it very likely

how much sample does a lab actually need for identity as well as purity

if the lab reports area percent without stating the wavelength, the number is less useful than it looks

integration difference

how do you tell co-elution from a clean single peak

while im here has anyone ever had a result where the mass was right and the purity was wrong

Assay note: JEEP lot B-0114 reported at 96.8% of label content.

thats co-elution

the first peak is the solvent. it is always the solvent

does retention time on its own tell you what the compound is

need more sample

within inter-lab range

follow up do you trust an area percent from a shallow gradient

nobody runs enough blanks, including me