CI Troubleshooting 3
85
High electron multiplier voltage
The electron multiplier voltage can range from a few hundred volts to 3,000 V.
If the CI autotune program consistently sets the electron multiplier voltage at
or above 2,600 V but can still find peaks and complete the tune, it may indicate
a problem.
The filament is worn out.
The CI filament may wear out without actually breaking. Check the Electron
Energy ramp; the curve should have a definite maximum with an inflection
point. If the curve is linear with a positive slope and no inflection point, and
the EMV is high, the filament has stretched to the point where it does not line
up with the hole in the ion source body, and most electrons are not getting into
the source.
Replace the filament.
The analyzer is not at the proper operating temperature.
Verify the ion source and quadrupole temperatures. The default source
temperature is 250 °C for PCI and 150 °C for NCI. The quadrupole
temperature is 150 °C for both CI modes.
The CI ion source is dirty.
Clean the ion source.
The electron multiplier (detector) is failing. Switch to EI mode and confirm.
Replace the electron multiplier.
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