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- Posts: 51
- Joined: Tue Jan 24, 2006 1:50 pm
So here is another question from the neophyte that I am.
We got a new LC MS installed two days ago (soo it has all the right specs at the miment) and I've been playing with it and I find the signals a bit too low to my liking.
Column: 150x4.6mm 5µm C18 - 40°C
Flow : 0.8ml/min
MS: DUIS
Scanning: 100 to 450 m/z in positive mode
Solvents: A H2O with 0.1% HCOOH, B: MeCN with 0.1% HCOOH (I tried with MeOH + 0.1% HCOOH with similar results).
Run: 5% B at 0 min - 95%B at 9.5 min. Pressure of about 75 bars
I'm trying to observe fluorinated esters and they are basically merely sticking out of the baseline...
Should I:
Get another column? (100x2.1mm 3um?)
Slow down the flow rate? To what? I guess I'll have to extend the run too...
Scan from 120 m/z? Is this a limitation that you can't see "small" molecules?
I could also start playing with the horizontal position of the spray nozzle, but I'm not sure ...
Thank you so much for any help you could offer to a newbie!