why does integration change the number so much
#hplc-massspec 2025-12-03
Wednesday30 messages7 participantstimes are UTC
Highlights from this day
- apob_over_ldl — does ms/ms actually prove identity or just make it very likely 22:26
- HPLC_Hank — how do you spot a deletion in a sequence from mass alone 22:43
- drawup_dee — baseline is drifting badly, is that the column or the mobile phase 22:55
- HPLC_Hank — while im here a warm transit can put a visible degradant peak on a chromatogram. that is what 11 days at ambient does 23:00
retention time is a hint
does ms/ms actually prove identity or just make it very likely
📉16
my peak has a shoulder on it, what does that usually mean
baseline drift on a gradient is normal. baseline drift on an isocratic hold is your column
integration difference
whats a normal gradient for a peptide this size
nobody runs enough blanks, including me
[edited]is a tailing factor of anything specific a problem
how do you spot a deletion in a sequence from mass alone
📉8🙏12🎉14
genuine question is monoisotopic or average mass the one on most certificates
coming back after 11 months, what changed in how you read these
is there any point running a blank if the sample is the question
oxidation is about plus 15.99 Da and is usually methionine or tryptophan
*Janoshik not the other one
baseline is drifting badly, is that the column or the mobile phase
the honest position is that hobby-level interpretation of a chromatogram is worth something but not much, i could be wrong
update on the earlier thing a shoulder on a peak is information, and usually bad information, anyway
pinch_not_stretchis there any point running a blank if the sample is the question oxidation is about…
while im here a warm transit can put a visible degradant peak on a chromatogram. that is what 11 days at ambient does
M = 4113.6
[M+2H]2+ = (4113.6 + 2.02) / 2 = 2057.8
[M+3H]3+ = (4113.6 + 3.02) / 3 = 1372.2
observed 1372.3 -> consistent🧊1🧪14📈3
how do you tell co-elution from a clean single peak
ms/ms sequencing is the only thing i would call identity. everything else is circumstantial
👍3❤️1🧪1
whats the void volume peak, is that always solvent
plus sixteen, is that always oxidation
i have a number at about a third of what i expected, is that a charge state
[edited]you need more sample for identity than for purity. plan for that when you post it, still working it out
if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic
thats a charge state
[edited]thats the solvent peak
why do two labs integrate the same peak differently
how would a truncation sequence show up
i was wrong about tailing factor. it is usually the injection or the pH, not the column