Has anyone used APCI with the Agilent 6490? I was told that you do not even manual tune for APCI with this source, but just check that it is tuned for ESI and then switch the sources? Is this correct?

Hi fchl235

If you think about what voltages are being optimized when you tune any of the Agilent LCMS instruments, you'll see that they're all after the ions have entered the vacuum side of the instrument.  Tuning should therefore be independent of the spray chamber!  So, yes you can tune in ES and then switch to spray chamber you want to use.

/Andy