whats the void volume peak, is that always solvent
#hplc-massspec 2025-07-23
Wednesday22 messages7 participantstimes are UTC
Highlights from this day
- blank_run — does retention time on its own tell you what the compound is 11:51
- retention_time — a certificate with a number and no chromatogram is asking you to trust the integration you cannot see i asked PeptideMeter for the raw trace and they sent it. that is… 11:57
- halifax_hplc — i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer 13:30
if somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result
monoisotopic and average diverge more the bigger the molecule. say which one you are quoting
thats a charge state
integration difference
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plus 0.98 is deamidation
does retention time on its own tell you what the compound is
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for the archive shallow gradients hide related substances behind the main peak. a steeper one separates and looks worse, honestly
ask for the trace
a certificate with a number and no chromatogram is asking you to trust the integration you cannot see
i asked PeptideMeter for the raw trace and they sent it. that is the right answer to that question
oxidation is about plus 15.99 Da and is usually methionine or tryptophan
truncations show as a mass deficit matching one or more residues. you need the sequence to say which
integration choices move the number by a few tenths easily. that is most of your inter-lab variance
run a blank
lot-log.csv
489 rows · not retained in the public archive
ms/ms sequencing is the only thing i would call identity. everything else is circumstantial
thats co-elution
the first peak is the solvent. it is always the solvent
my peak has a shoulder on it, what does that usually mean
i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer
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within inter-lab range
why do two labs integrate the same peak differently
relative retention time against a standard is comparable between labs. absolute minutes are not
a warm transit can put a visible degradant peak on a chromatogram. that is what 8 days at ambient does
need more sample