98 5977 Series MSD Operation Manual
4 Operating in Chemical Ionization (CI) Mode
To Pump Down the MSD in CI Mode
This procedure assumes that the instrument will eventually be PCI tuned
using methane after the system is stable.
Procedure
1 Follow the instructions for the EI MSD. See “To Pump Down the MSD in EI
Mode” on page 84.
After the software prompts you to turn on the interface heater and GC
oven, perform the following steps.
2 In the Manual Tune dialog, click the Values tab to monitor that the pressure
is decreasing (Hi-Vac gauge option installed).
3 In the Manual Tune dialog, click the CI Gas tab, then in the Valve Settings area
close Gas Valve A, Gas Valve B, and the ShutOff Valve.
4 Verify that PCICH4.U is loaded (top left in Manual Tune dialog) and click the
Values tab to accept the temperature setpoints.
Always start up and verify system performance in PCI mode before
switching to NCI.
5 Set the GC/MSD interface to 280 °C.
6 Set Gas A (methane) to 20%.
7 Let the system bake out and purge for at least 2 hours. If you will be
running NCI, for best sensitivity, bake out the MSD overnight.
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