Installation manual

120 5975 Series MSD Operation Manual
4 Operating in Chemical Ionization (CI) Mode
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
(Figure 31). 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 page 76.
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.