CI Troubleshooting 3
75
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 the MSD 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 71.
If the MSD was recently switched from EI to CI
• Isolation tip not installed
• No reagent gas flow
• Analyzer not sealed (big air leak)
• Wrong tune file loaded or tune file corrupted
• Ion source not assembled or connected correctly
• Wrong reagent gas selected for the tune file (looking for wrong ions)
No PFDTD peaks in PCI
• Incorrect reagent gas. There are no PCI PFDTD peaks created with
isobutane or ammonia. Switch to methane.
• Analyzer not sealed (big air leak)
• No calibrant in vial
• Defective calibration valve(s)
• Air leak in carrier or reagent gas path
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