214nm sees the amide backbone so it sees everything. 280 only sees aromatics
[edited]weights-monthly.csv
929 rows · not retained in the public archive
#hplc-massspec 2026-01-24
Saturday22 messages7 participantstimes are UTC
Highlights from this day
- two_four_ceiling — is there any point running a blank if the sample is the question truncations show as a mass deficit matching one or more residues. you need the sequence to say which 18:56
- tesa_tess — why does integration change the number so much 19:37
- tesa_tess — update from 1 months ago: switched to asking for the chromatogram rather than the number and it changed everything, your mileage will differ 20:35
- seven_five_sweet — does retention time on its own tell you what the compound is update from 5 months ago: switched to asking for the chromatogram rather than the number and it changed… 20:40
- still_here_2024 — oxidation is about plus 15.99 Da and is usually methionine or tryptophan 20:53
thats a charge state
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is there any point running a blank if the sample is the question
truncations show as a mass deficit matching one or more residues. you need the sequence to say which
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can you tell a dimer from the chromatogram alone
if somebody says they ran a mass spec and does not show you a spectrum, that is a claim, not a result
relative retention time against a standard is comparable between labs. absolute minutes are not
deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant
tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5, thats just me
why does integration change the number so much
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ms/ms sequencing is the only thing i would call identity. everything else is circumstantial, n of 1 obviously
how do you spot a deletion in a sequence from mass alone
ask for the trace
thats the solvent peak
update from 1 months ago: switched to asking for the chromatogram rather than the number and it changed everything, your mileage will differ
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plus sixteen, is that always oxidation
has anyone ever had a result where the mass was right and the purity was wrong
does retention time on its own tell you what the compound is
update from 5 months ago: switched to asking for the chromatogram rather than the number and it changed everything
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*Medutest not the other one
oxidation is about plus 15.99 Da and is usually methionine or tryptophan
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monoisotopic and average diverge more the bigger the molecule. say which one you are quoting, take that with a pinch of salt
do the arithmetic
need more sample
why do two labs integrate the same peak differently