Operating in Chemical Ionization (CI) Mode 4
5977 Series MSD Operation Manual 113
To Perform an NCI Autotune (Methane Reagent Gas)
Procedure
1 From the Tune and Vacuum Control view, load NCICH4.U (or an existing
tune file for the reagent gas you are using).
2 From the Setup menu select the CI Tune Wizard and follow the system
prompts.
Accept the default temperature and other settings.
If you use an existing tune file, be sure to save it with a new name if you
don’t want to overwrite the existing values.
3 Under the Tune menu, click CI Autotune.
There are no tune performance criteria. If autotune completes, it passes (See
Figure 19 on page 114). If the tune sets the electron multiplier voltage
(EMVolts) at or above 2600 V, however, you may not be able to acquire data
successfully if your method sets EMVolts to “+400” or higher.
CAUTION
Always verify MSD performance in EI before switching to CI operation. See “To Verify
System Performance” on page 71. Always set up the CI MSD in PCI with methane as
the reagent gas first, even if you are going to be using a different reagent gas or going
to run NCI.
CAUTION
Avoid tuning unless absolutely necessary; this will minimize PFDTD background noise
and help prevent ion source contamination.
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