why do two labs integrate the same peak differently
#hplc-massspec 2025-03-19
Wednesday19 messages6 participantstimes are UTC
Highlights from this day
- ferritin_fay — baseline is drifting badly, is that the column or the mobile phase 16:11
- ms_ms_mira — whats a normal gradient for a peptide this size 16:22
- ferritin_fay — unrelated but retention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily relative retention time against a standard is… 18:18
- VialBot — Recon calculator: 15mg in 1.5ml = 4mg/ml. 19:08
- VialBot — New independent result logged — QYB, lot E-2205, purity 99.4% (Janoshik). 20:26
whats a plus one dalton shift usually
ms/ms or it isnt identity
baseline is drifting badly, is that the column or the mobile phase
🎉7
plus 16 is oxidation
retention time is a hint
whats a normal gradient for a peptide this size
👀1⚠️1🙏3
right so co-elution is the failure mode that a beautiful single peak is most likely to be hiding
integration difference
while im here i have a number at about a third of what i expected, is that a charge state
unrelated but retention time is a hint, not a fingerprint. two different peptides can co-elute perfectly happily
relative retention time against a standard is comparable between labs. absolute minutes are not
you need more sample for identity than for purity. plan for that when you post it
i asked Janoshik for the raw trace and they sent it. that is the right answer to that question
plus sixteen, is that always oxidation
thats the solvent peak
Recon calculator: 15mg in 1.5ml = 4mg/ml.
do the arithmetic
has anyone ever had a result where the mass was right and the purity was wrong
do you trust an area percent from a shallow gradient
New independent result logged — QYB, lot E-2205, purity 99.4% (Janoshik).