4
Operating in Chemical Ionization (CI) Mode
General Guidelines
• Always use the highest purity methane (and other reagent gases, if
• Always verify the MSD is performing well in EI mode before switching to CI.
• Make sure the CI ion source and GC/MSD interface tip seal are installed.
• Make sure the reagent gas plumbing has no air leaks. This is determined in
• Make sure the reagent gas inlet line is equipped with gas purifiers (not
90
applicable). Methane must be at least 99.9995% pure.
See
"To Verify System Performance"
PCI mode, checking for m/z 32 after the methane pretune.
applicable for ammonia).
on page 71.
5977 Series MSD Operation Manual