3-26 Tuning the Instrument
Setting up and purging the CI gas lines
Before introducing the CI reagent gas, the internal CI reagent gas lines must
be purged of air.
To set up and purge the CI gas line:
1. Ensure the CI inner source is correctly installed.
See also: Installing the EI/CI inner source on page 2-4.
2. Ensure all the CI gas bottle supply connections are free of leaks.
See also: To location the CI gas connection, see Gas inlet connections on
page 1-19.
3. In the Tune window, click Ion Mode > CI+.
4. Ensure a cylinder of methane (or other CI gas) is connected to the CI gas
inlet on the rear panel of the instrument.
5. Ensure there are no leaks on the CI gas line connections.
See also: Inspecting the CI gas line for leaks on page 10-48.
6. Ensure the main outlet valve on the cylinder is closed.
7. In the Tune window Inlet tab, click CI Purge.
The CI line is now be evacuated. If the backing line pressure does not
recover, look for leaks in the internal or external CI inlet or pump lines.
Introducing CI reagent gas
To introduce the CI reagent gas:
1. In the Tune window Inlet tab, ensure that the CI Gas check box is
cleared so that the CI gas valve is closed.
2. Open the cylinder and set the methane pressure to 10 psi (0.68 bar).
3. In the Tune window Inlet tab click CI Gas.
4. Monitor the source pressure on the Vacuum Monitor menu and increase
the CI flow valve slider to achieve a source pressure of 1 to 2 e-4 mbar.
5. In the Engineer tab, reset the solvent trip level.
Result: The filament is turned on at this increased pressure.
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