5 Operating in CI Mode
To Perform a PCI Autotune (Methane Only)
5977C GC/MSD Operating Manual 131
To Perform a PCI Autotune (Methane Only)
Procedure
1 Verify that the MSD performs correctly in EI mode first. (See “To Verify EI
System Performance” on page 104.)
2 From the Tune and Vacuum Control view, load the PCICH4.U tune file or an
existing tune file for the reagent gas you are using.
If you use an existing tune file, be sure to save it with a new name if you do
not want to overwrite the existing values.
3 Accept the default settings.
4 Perform methane setup. (See “To Set Up Methane Reagent Gas Flow” on
page 126.)
5 Under the Tune menu, click CI Autotune.
There are no tune performance criteria. If autotune completes, it passes. (See
Figure 43 on page 132.) If the tune sets the EMV at or above 2,600 V, however,
you may not be able to acquire data successfully if your method sets EMV to
“+400” or higher.
The autotune report contains information about air and water in the system. (See
“PCI autotune report” on page 132.)
The 19/29 ratio shows the abundance of water.
The 32/29 ratio shows the abundance of oxygen.
Always verify MSD performance in EI before switching to CI operation. Always
set up the CI MSD in PCI first, even if you are going to run NCI.
Avoid tuning more often than is absolutely necessary; this will minimize PFDTD
background noise and help prevent ion source contamination.
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