is retention time alone ever enough for identity
Thread · #hplc-massspec · 2026-01-16
column age moves retention times slowly and predictably
Spun off from a message in #hplc-massspec on 2026-01-16. 13 messages, 4 participants.
The message this came from
- no_escrow_nate — column age moves retention times slowly and predictably, which is why a lab compares against its own standard on the day, the summary already judged it. fragments are better 15:11
column age moves retention time and does not usually move the area percent much, happy to be corrected on that
baseline is drifting badly, is that the column or the mobile phase, writing this up so want it right
why does integration change the number so much, or has that changed
if you post a trace, post the axes. a chromatogram without a time axis is a shape, one sample, one lab
relative retention time against a standard is comparable between labs. absolute minutes are not
circling back retention time is a hint. identity comes from the mass, and preferably from fragmentation as well
does the injection volume change the area percent or just the height
need more sample
about area percent again is esi or maldi more common on the certs you see
chromatography question a difference of plus sixteen is oxygen and plus point nine eight is a deamidation, and those two cover most of what you will see
pedantry about identity the retention time on its own means nothing across two labs. the relative order of the peaks means quite a lot
that tracks, integration is a judgement then