5 Operating in CI Mode
To Pumpdown the MSD in CI Mode
120 5977C GC/MSD Operating Manual
To Pumpdown 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 Pumpdown the MSD” on
page 112.)
After the software prompts you to turn on the GC/MSD 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. (See Table 11 on page 119.)
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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