62 Troubleshooting and Maintenance Manual
3 CI Troubleshooting
Signal-Related Symptoms
This section describes symptoms related to the signal. The symptom may be
too much signal, too little signal, a noisy signal, or an incorrect signal.
Signal-related symptoms are generally observed during tuning but may also be
observed during data acquisition.
Error messages in autotune due to insufficient signal may vary.
The following symptoms are covered in more detail in this section:
• No peaks. See page 62.
• No or low reagent gas signal. See page 64.
• No or low PFDTD signal. See page 66.
• Excessive noise. See page 67.
• Low signal-to-noise ratio. See page 67.
• Large peak at m/z 19. See page 68.
• Peak at m/z 32. See page 69.
No peaks
When troubleshooting “no peaks” it is important to specify what mode of
operation is being used and what expected peaks are not being seen. Always
start with methane PCI and verify presence of reagent ions.
No reagent gas peaks in PCI
If MS has been working well and nothing seems to have been changed
• Wrong tune file loaded, or tune file corrupted
• Wrong ion polarity (there are no reagent ions visible in NCI)
• No reagent gas flow; look for background ions and check pressure
• Wrong reagent gas selected for the tune file (looking for wrong ions)
• Large air leak
• Dirty ion source
• Poor vacuum (pump problem). See page 58.
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