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3
CI Troubleshooting
Large peak at m/z 238 in NCI OFN spectrum
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No or low reagent gas signal
If you have just installed the CI ion source and have an air leak or large amounts
of water in the system and have run one or more autotunes, the ion source is
probably dirty now.
Fix the air leak. Clean the ion source. Then bake out for two hours before tuning.
See the Agilent 7250 Accurate-Mass Quadrupole Time-of-Flight GC/MS System
Operating Manual.
The wrong reagent gas is flowing.
Turn on the correct reagent gas for your tune file.
Ion polarity is set to Negative. No reagent gas ions are formed in NCI.
Switch to Positive ionization mode.
The reagent gas flow is set too low.
Increase the reagent gas flow.
Reagent gas supply tubing is blocked, kinked, pinched, or disconnected.
Inspect and, if necessary, repair or replace the reagent gas supply tubing.
Carbon has built up on the filament or filament has sagged out of
alignment.
Inspect the filament. If necessary, replace the filament.
Too much air or water in the system.
Run an air and water check. See the software online help for additional
information.
The signal cable is not connected.
Check and, if necessary, reconnect the signal cable.
60
Look for background ions: 35 (Cl
Find and fix your small air leak
7250 Accurate-Mass Q-TOF Troubleshooting and Maintenance Manual
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), and 235 (ReO3
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Table of Contents
Troubleshooting
