84 Operation Manual
4 Operating in Chemical Ionization (CI) Mode
To Switch from the EI Mode to CI Mode
Notes for Table 8:
• N/A Not available.
• Abundance target Adjust higher or lower to get desired
signal abundance. Higher signal abundance also gives higher
noise abundance.
• Peakwidth target Higher peakwidth values give better
sensitivity, lower values give better resolution.
• Maximum emission current Optimum emission current
maximum for NCI is very compound-specific and must be
selected empirically. Optimum emission current for
pesticides, for example, may be about 200 µA.
Table 8 Default Tune Control Limits, used by CI autotune only
Reagent gas Methane Ammonia
Ion polarity Positive Negative Positive Negative
Abundance target 1x10
6
1x10
6
N/A 1x10
6
Peakwidth target 0.7 0.7 N/A 0.7
Maximum repeller 4 4 N/A 4
Maximum emission
current, µA
240 50 N/A 50
Max electron energy, eV 240 240 N/A 240
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