retention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily
#hplc-massspec 2025-09-12
Friday10 messages3 participantstimes are UTC
Highlights from this day
- endotoxin_ed — a shoulder on a peak is information, and usually bad information retention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily 19:22
- endotoxin_ed — while im here is there any point running a blank if the sample is the question if the number you are staring at is a third of what you expected, do the charge state… 19:31
- cat_on_the_tray — integration choices move the number by a few tenths easily. that is most of your inter-lab variance 19:43
- cat_on_the_tray — coming back to this tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5 19:45
i have a number at about a third of what i expected, is that a charge state
ms/ms sequencing is the only thing i would call identity. everything else is circumstantial
a shoulder on a peak is information, and usually bad information
retention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily
while im here is there any point running a blank if the sample is the question
if the number you are staring at is a third of what you expected, do the charge state arithmetic before you panic
monoisotopic and average diverge more the bigger the molecule. say which one you are quoting
whats a plus one dalton shift usually
integration choices move the number by a few tenths easily. that is most of your inter-lab variance
within inter-lab range
coming back to this tirzepatide is about 4813.5 Da, so 2+ is near 2407.8 and 3+ near 1605.5
🎉4