whats a plus one dalton shift usually
#hplc-massspec 2026-06-16
Tuesday26 messages7 participantstimes are UTC
Highlights from this day
- VialBot — New independent result logged — TFC, lot C-4402, purity 99.2% (PeptideMeter). 18:56
- mira_pins — oxidation is about plus 15.99 Da and is usually methionine or tryptophan you need more sample for identity than for purity. plan for that when you post it 19:37
- VialBot — On this day 9 years ago this channel logged 58 messages. 19:48
- retention_time — i asked PeptideMeter for the raw trace and they sent it. that is the right answer to that question 20:03
run a blank
nobody runs enough blanks, including me
ms/ms or it isnt identity
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a shoulder on a peak is information, and usually bad information
the first peak is the solvent. it is always the solvent
co-elution is the failure mode that a beautiful single peak is most likely to be hiding
retention time is a hint
New independent result logged — TFC, lot C-4402, purity 99.2% (PeptideMeter).
the honest position is that hobby-level interpretation of a chromatogram is worth something but not much, not advice obviously
how would a truncation sequence show up
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follow up baseline is drifting badly, is that the column or the mobile phase
i was wrong about tailing factor. it is usually the injection or the pH, not the column
ok so 214nm sees the amide backbone so it sees everything. 280 only sees aromatics
ok so is there any point running a blank if the sample is the question
plus 16 is oxidation
show me the spectrum
oxidation is about plus 15.99 Da and is usually methionine or tryptophan
you need more sample for identity than for purity. plan for that when you post it
fridge-temps.csv
819 rows · not retained in the public archive
need more sample
is a tailing factor of anything specific a problem
ms/ms sequencing is the only thing i would call identity. everything else is circumstantial
co-elution is the failure mode that a beautiful single peak is most likely to be hiding
do the arithmetic
integration difference
a warm transit can put a visible degradant peak on a chromatogram. that is what 24 days at ambient does
On this day 9 years ago this channel logged 58 messages.
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i asked PeptideMeter for the raw trace and they sent it. that is the right answer to that question
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how much sample does a lab actually need for identity as well as purity