Download GC/MS : A Practical User's Guide

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APPENDIX B: GC/MS TROUBLESHOOTING QUICK REFERENCE
Problem 13: Calibration gas’ 69 peak position moving. Poor 70 mass
resolution.
Cause a: System grounding problem.
Treatment: Ground analyzer unit to control interface. Float the
computer ground.
Cause b: Ion source is dirty.
Treatment: Shut down system. Clean the source.
Problem 14: No calibration gas peaks.
Cause a: Cal gas valve not open.
Treatment: Open cal gas valve.
Cause b: Calibration gas solenoid valve stuck open. All calibration gas
evaporated.
Treatment: Have solenoid replaced. Put fresh PFBTA in the cal
gas vial.
B.5 MS SENSITIVITY AND DETECTOR PROBLEMS
Problem 15: Analysis sensitivity has decreased.
Cause a: Background has increased.
Treatment: Check column bleed, septum bleed, pump oil, and ion
source contamination.
Cause b: Detector needs replacement.
Treatment: EM voltage is over 3500 V to see cal gas 502.
Replace detector.