6 Operating in CI Mode
To Pumpdown and Switch from EI to CI Mode
146 7000/7010 Series TQ GC/MS Operating Manual
14 Click Autotune to start the autotune. At the completion of the autotune a
Tune Report is printed.
15 Review the Tune Report. If the results are acceptable, save the autotune by
clicking the Files and Report tab, then click Save. Default tune control limits
are shown in Table 13.
Notes for Table 13:
• N/A: Not available.
• Abundance target: Adjust higher or lower to get desired signal abundance.
Higher signal abundance also gives higher noise abundance. This is adjusted
for data acquisition by setting the EMV in the method.
• 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 13 Default Tune Control Limits, used by CI autotune only
Reagent gas Methane Ammonia
Ion polarity Positive Negative Positive Negative
Abundance target 1×10
6
1×10
6
N/A 1×10
6
Peak width 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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