ISQ User Guide - Write Frame of Mind

7 Optimizing Your Method
Modifying an Automatic Tune
7. Configure the Ion Source tab.
• Ionization Mode and Ion Polarity—Use this pull-down menu to select a mode:
– Select EI+ to run a tune in Electron Ionization (EI) mode.
– Select CI+ to run a tune in Chemical Ionization (CI) mode and look at positive
ions.
– Select CI- to run a tune in CI mode and look at negative ions.
• CI Gas Type (only enabled if you select CI+ or CI-)—Use this pull-down menu to
select a gas type, but make sure your selection is the reagent gas attached to your
system and that the correct gas port is selected. Methane is commonly used for CI+.
Other gases will change the efficiency and energy of the ionization process.
Note When changing CI gas types or gas port, there is a two minute delay while the
reagent gas is purging. During this time, the Busy light will be lit and you have to wait
until the light goes off before using the ISQ software.
• CI Gas Flow (enabled when you select a CI Gas Type)—Use this field to enter the
flow rate of your CI gas.
• Emission Current—Use this field to define the emission current you use to run
subsequent tunes, but not the emission current that is used for data acquisition.
– Tune File—Select this option to use the value in the tune file you selected in the
General tab.
– Default—Select this option to use the default emission current, which is 50 μA.
80 ISQ User Guide Thermo Scientific