To Set Up Methane Reagent Gas Flow - Agilent Technologies G7035A Operation Manual

4
Operating in Chemical Ionization (CI) Mode

To Set Up Methane Reagent Gas Flow

The reagent gas flow must be adjusted for maximum stability before tuning the
CI system. Do the initial setup with methane in positive chemical ionization
(PCI) mode. No flow adjustment procedure is available for NCI, as no negative
reagent ions are formed.
Adjusting the methane reagent gas flow is a three-step process: setting the
flow control, pretuning on the reagent gas ions, and adjusting the flow for
stable reagent ion ratios, for methane, m/z 28/27.
Your data system will prompt you through the flow adjustment procedure.
Procedure
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After the system has been switched from EI to CI mode, or vented for any other reason,
CA UT IO N
the MSD must be baked out for at least 2 hours before tuning.
Continuing with CI autotune if the MSD has an air leak or large amounts of water will
result in severe ion source contamination. If this happens, you need to vent the MSD
and clean the ion source.
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104
Using an EI ion source, perform the standard autotune, save the report, and
note the reported pressure. See
Vent the system. See
Install the CI ion source. See
Pump out the system. See
page 98.
Wait until the pressure is near the previously recorded pressure for the EI
autotune. See "To Monitor CI Mode High Vacuum Pressure"
Select Bake out MSD from the Manual Tune view Execute menu to display the
Specify Bake Out parameters dialog. Set for a minimum time of 2 hours, adjust
the other parameters, and click OK to begin the bake out.
Select Methane Pretune from the Setup menu and follow the system
prompts. See the MassHunter online help for additional information.
The methane pretune tunes the instrument for optimum monitoring of the
ratio of methane reagent ions m/z 28/27.
"To Tune the MSD in EI Mode"
"Venting the MSD" on page 57.
"To Install the CI Ion Source"
"To Pump Down the MSD in CI Mode"
on page 167.
on page 117.
5977 Series MSD Operation Manual
on page 69.
on