Installation manual

Operating in Chemical Ionization (CI) Mode 4
5975 Series MSD Operation Manual 105
Notes for Table 16:
• N/A Not available. There are no PFDTD ions formed in PCI with any
reagent gas but methane, hence, CI autotune is not available with these
configurations.
• Ion polarity Always set up in PCI with methane first, then switch to your
desired ion polarity and reagent gas.
• 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 16 Default Tune Control Limits, used by CI autotune only
Reagent gas Methane Isobutane Ammonia
Ion polarity Positive Negative Positive Negative Positive Negative
Abundance target 1x10
6
1x10
6
N/A 1x10
6
N/A 1x10
6
Peakwidth target 0.6 0.6 N/A 0.6 N/A 0.6
Maximum repeller 4 4 N/A 4 N/A 4
Maximum emission
current, µA
240 50 N/A 50 N/A 50
Max electron energy, eV 240 240 N/A 240 N/A 240