why do two labs integrate the same peak differently
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#hplc-massspec 2026-02-15
Sunday25 messages7 participantstimes are UTC
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coming back after 22 months, what changed in how you read these
follow up does ms/ms actually prove identity or just make it very likely
Purity check: no report on file for lot A-2601. Nothing logged either way.
if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic
unrelated but i have a number at about a third of what i expected, is that a charge state
need more sample
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co-elution is the failure mode that a beautiful single peak is most likely to be hiding, your mileage will differ
right so a warm transit can put a visible degradant peak on a chromatogram. that is what 10 days at ambient does
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i asked Janoshik for the raw trace and they sent it. that is the right answer to that question
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retention time is a hint
a dimer usually shows up late and at roughly double the mass. the chromatogram alone will not tell you, happy to be corrected
ms/ms or it isnt identity
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the honest position is that hobby-level interpretation of a chromatogram is worth something but not much
within inter-lab range
does retention time on its own tell you what the compound is
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i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer
coming back to this truncations show as a mass deficit matching one or more residues. you need the sequence to say which
plus 0.98 is deamidation
monoisotopic and average diverge more the bigger the molecule. say which one you are quoting
a shoulder on a peak is information, and usually bad information
while im here is there any point running a blank if the sample is the question
right so semaglutide is about 4113.6 Da. [M+2H]2+ lands near 2057.8, [M+3H]3+ near 1372.2
coming back to this ms/ms sequencing is the only thing i would call identity. everything else is circumstantial
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how would a truncation sequence show up