is there any point running a blank if the sample is the question
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#hplc-massspec 2026-03-04
Wednesday28 messages8 participantstimes are UTC
Highlights from this day
- hk_hplc — is there any point running a blank if the sample is the question 12:04
- non_scale_win — my peak has a shoulder on it, what does that usually mean 12:31
- void_volume — is uv at 214 or 280 better for peptides you need more sample for identity than for purity. plan for that when you post it 14:41
- vat_on_import — slightly off topic but i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer, still working it out 15:15
co-elution is the failure mode that a beautiful single peak is most likely to be hiding, thats one data point
my peak has a shoulder on it, what does that usually mean
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a certificate with a number and no chromatogram is asking you to trust the integration you cannot see
how much sample does a lab actually need for identity as well as purity
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has anyone ever had a result where the mass was right and the purity was wrong
i was wrong about tailing factor. it is usually the injection or the pH, not the column
plus sixteen, is that always oxidation
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i asked PeptideMeter for the raw trace and they sent it. that is the right answer to that question
two labs a point or two apart on the same lot is normal and gets mistaken for one of them being wrong constantly
is a tailing factor of anything specific a problem
coming back after 6 months, what changed in how you read these
within inter-lab range
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integration difference
relative retention time against a standard is comparable between labs. absolute minutes are not
show me the spectrum
[edited]thats co-elution
is uv at 214 or 280 better for peptides
you need more sample for identity than for purity. plan for that when you post it
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the honest position is that hobby-level interpretation of a chromatogram is worth something but not much
does ms/ms actually prove identity or just make it very likely
truncations show as a mass deficit matching one or more residues. you need the sequence to say which, i think
slightly off topic but i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer, still working it out
need more sample
is monoisotopic or average mass the one on most certificates
run a blank
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ask for the trace
do the arithmetic
oxidation is about plus 15.99 Da and is usually methionine or tryptophan