48 5977B Series MSD Troubleshooting and Maintenance Manual
2 General Troubleshooting
High mass sensitivity is poor
This refers to a condition where the absolute abundance at the upper end of
the mass range is poor. Absolute abundance should not be confused with the
relative abundance (percentage) of m/z 502 to m/z 69. Sensitivity at high
masses can be excellent even if the relative abundance of m/z 502 is low.
• Wrong tune program
• Wrong tune file
• Repeller voltage is too low
• Not enough time for the MSD to warm up and pump down
• Analyzer chamber pressure is too high
• Column (carrier gas) flow is too high
• Poor filament operation
• Dirty ion source
• Air leak
• Incorrect DC polarity on the quadrupole mass filter
• No voltage to the extractor lens (is using an extractor EI ion source)
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