does retention time on its own tell you what the compound is
#hplc-massspec 2026-02-06
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oxidation is about plus 15.99 Da and is usually methionine or tryptophan
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quick one if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic
two labs a point or two apart on the same lot is normal and gets mistaken for one of them being wrong constantly
show me the spectrum
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plus sixteen, is that always oxidation
you need more sample for identity than for purity. plan for that when you post it
is a tailing factor of anything specific a problem
a warm transit can put a visible degradant peak on a chromatogram. that is what 16 days at ambient does
truncations show as a mass deficit matching one or more residues. you need the sequence to say which
the first peak is the solvent. it is always the solvent, take that with a pinch of salt
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ms/ms sequencing is the only thing i would call identity. everything else is circumstantial, n of 1 obviously
integration choices move the number by a few tenths easily. that is most of your inter-lab variance, i could be wrong
Assay note: Homopeptide lot B-0329 reported at 97.4% of label content.
do the arithmetic
is uv at 214 or 280 better for peptides
ask for the trace