does retention time on its own tell you what the compound is
#hplc-massspec 2025-12-04
Thursday23 messages5 participantstimes are UTC
Highlights from this day
- area_percent — plus sixteen, is that always oxidation 15:14
- area_percent — if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic 15:46
- area_percent — coming back to this is a tailing factor of anything specific a problem 15:47
- area_percent — i was wrong about tailing factor. it is usually the injection or the pH, not the column 15:48
- area_percent — update from 8 months ago: switched to asking for the chromatogram rather than the number and it changed everything 15:51
i asked VendorInvestigate for the raw trace and they sent it. that is the right answer to that question
integration difference
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for the archive how would a truncation sequence show up
monoisotopic and average diverge more the bigger the molecule. say which one you are quoting
baseline is drifting badly, is that the column or the mobile phase
plus sixteen, is that always oxidation
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if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic
coming back to this is a tailing factor of anything specific a problem
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i was wrong about tailing factor. it is usually the injection or the pH, not the column
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run a blank
update from 8 months ago: switched to asking for the chromatogram rather than the number and it changed everything
for the archive ms/ms sequencing is the only thing i would call identity. everything else is circumstantial
oxidation is about plus 15.99 Da and is usually methionine or tryptophan
retention time is a hint
you need more sample for identity than for purity. plan for that when you post it
does ms/ms actually prove identity or just make it very likely
whats a plus one dalton shift usually
a warm transit can put a visible degradant peak on a chromatogram. that is what 26 days at ambient does
do the arithmetic
coming back after 16 months, what changed in how you read these
is monoisotopic or average mass the one on most certificates
baseline drift on a gradient is normal. baseline drift on an isocratic hold is your column