[mrniceguy]

We have been trying to calibrate a NanoESI source QTOF Premier. Glu-Fib at 500 fmol/ul was flowed by infusion and fragmented with collision energy between 20-25. We did calibrate following the manual but they have shown unmatched. We found all parent and fragment ions were hugely shift about two daltons, so we  manully reassigned peaks and accepted. However, when re-aquired glu-fib again, there still be mass shift. Anybody has suggestion what should I figure out this issue? I really appreciate any help you can provide.

Thanks

[Arkcon]

I have no specific help, but tell us clearly:  You identified the known M/Z for some peaks out of spec. Then you ran again, and the peaks misidentified.  Did your recalibration not get saved?  Or was it saved, and the peaks drifted more?  What's the window on M/Z for such an instrument?  I'd like to assume its 1 AMU, but I could be expected too much, so maybe you are too?

[MOTOBALL]

Perhaps this instrument is sensitive to temperature fluctuations.  If so,.

1) Make sure ambient lab. temperature is constant (no HVAC vents close-by)

2) cycle the instrument through the MS scan for half-hour to warm up the electronics and allow to stabilize.

3) Take the calibration scans.