ask for the trace
#hplc-massspec 2024-09-29
Sunday17 messages5 participantstimes are UTC
Highlights from this day
- quiet.hours — sorry to jump in is monoisotopic or average mass the one on most certificates 21:41
- area_percent — a dimer usually shows up late and at roughly double the mass. the chromatogram alone will not tell you 21:44
- quiet.hours — do you trust an area percent from a shallow gradient ms/ms sequencing is the only thing i would call identity. everything else is circumstantial 21:49
- deamidation — two labs a point or two apart on the same lot is normal and gets mistaken for one of them being wrong constantly if the number you are staring at is a third of what… 21:52
- area_percent — unrelated but i was wrong about tailing factor. it is usually the injection or the pH, not the column 22:23
tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5
thats the solvent peak
sorry to jump in is monoisotopic or average mass the one on most certificates
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how much sample does a lab actually need for identity as well as purity
a dimer usually shows up late and at roughly double the mass. the chromatogram alone will not tell you
shallow gradient
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do you trust an area percent from a shallow gradient
ms/ms sequencing is the only thing i would call identity. everything else is circumstantial
two labs a point or two apart on the same lot is normal and gets mistaken for one of them being wrong constantly
if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic
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plus 16 is oxidation
run a blank
[edited]unrelated but i was wrong about tailing factor. it is usually the injection or the pH, not the column
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is a tailing factor of anything specific a problem
is there any point running a blank if the sample is the question
need more sample
the first peak is the solvent. it is always the solvent
relative retention time against a standard is comparable between labs. absolute minutes are not