is uv at 214 or 280 better for peptides
#hplc-massspec 2025-10-05
Sunday18 messages5 participantstimes are UTC
Highlights from this day
- sharps_comedy — i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer 19:12
- sharps_comedy — is a tailing factor of anything specific a problem 19:13
- HPLC_Hank — coming back to this can you tell a dimer from the chromatogram alone baseline drift on a gradient is normal. baseline drift on an isocratic hold is your column 19:56
- area_percent — truncations show as a mass deficit matching one or more residues. you need the sequence to say which 20:09
- warsaw_vial — update on the earlier thing a dimer usually shows up late and at roughly double the mass. the chromatogram alone will not tell you 22:19
i have a number at about a third of what i expected, is that a charge state
i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer
is a tailing factor of anything specific a problem
👍18📉2✅13
thats a charge state
integration difference
i asked Medutest for the raw trace and they sent it. that is the right answer to that question
relative retention time against a standard is comparable between labs. absolute minutes are not
baseline is drifting badly, is that the column or the mobile phase
214nm sees the amide backbone so it sees everything. 280 only sees aromatics
how do you spot a deletion in a sequence from mass alone
coming back to this can you tell a dimer from the chromatogram alone
baseline drift on a gradient is normal. baseline drift on an isocratic hold is your column
co-elution is the failure mode that a beautiful single peak is most likely to be hiding
truncations show as a mass deficit matching one or more residues. you need the sequence to say which
[edited]tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5
why do two labs integrate the same peak differently
integration choices move the number by a few tenths easily. that is most of your inter-lab variance
update on the earlier thing a dimer usually shows up late and at roughly double the mass. the chromatogram alone will not tell you