Preparing for FI operation 3-33
6. In the TDC Settings dialog box Data pane, set the Veff value to display
the correct mass in the peak display.
See also: Setting up nominal mass on page B-47.
7. To obtain the best intensity of the m/z 451.97 ion, retune the following
parameters in the Tune window, CI Tune tab, Beam Steering, Focus1,
Focus2, and, Focus3.
Tip: The CI gas pressure can be optimized as this parameter can often be
compound dependant.
Note: There is little low mass background in this technique, and
therefore it should not be necessary to consider ions of low mass in terms
of saturation while tuning.
8. Continue to tune the instrument until you have maximized the intensity
of the peak.
Note: Maintain the intensity of the peak at approximately 1000 counts
per second in continuum to avoid saturation.
9. See also:
• General considerations for tuning on page G-6
• Dead time correction on page B-49
• Effects of saturation on peak shape on page B-51
10. Adjust the CI gas pressure if necessary to obtain best sensitivity.
Turning off CI gas
To turn off CI gas
In the Tune window Inlet tab, clear the CI Gas check box.
At the end of CI operation, the rotary pump must be gas ballasted for 30
minutes.
See also: Gas-ballasting the rotary pump on page 10-5.
Preparing for FI operation
For a detailed description of how to tune the instrument for FI operation, see
Chapter 9 Tuning the Instrument.
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