Poor Sensitivity; Poor Repeatability - HP 5973 Hardware Manual

Troubleshooting the MSD
3
Chromatographic symptoms

Poor sensitivity

• Incorrect tuning
• Tune file that does not match the type of analysis
• Repeller voltage is too low
• Incorrect temperatures (oven, GC/MSD interface, ion source, or mass filter)
• Incorrect sample concentration
• Leaking injection port*
• Dirty injection port
• Incorrect split ratio
• Purge off time in splitless mode is too short
• Excessive pressure in the MSD
• Dirty ion source
• Air leak
• Poor filament operation
• Detector (HED electron multiplier) is not working correctly
• Incorrect mass filter polarity
* This could cause a fault condition in the GC that would prevent the GC from
operating.

Poor Repeatability

• Dirty syringe needle
• Dirty injection port
• Leaking injection port*
• Injection is too large
• Loose column connections
• Variations in pressure, column flow, and temperature
• Dirty ion source
• Loose connections in the analyzer
• Ground loops
* This could cause a fault condition in the GC that would prevent the GC from
operating.
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