
Mass
Spectrometer
PlasmaQuant MS Series
140
Ion optics elements
Effect of lens on
sensitivity in ppq mode
(high sensitivity)
Effect of lens on
sensitivity in ppb
mode (normal
sensitivity)
Range
(Volts)
Tips for the operator
Extraction lens #3
Moderate
Moderate
-1000 to 0
Changes in extraction lens #3
will induce a need for a change
in corner lens voltage in the
same direction. For example,
an increase in negative voltage
applied to extraction lens#3
will require an increase in
negative voltage applied to the
corner lens.
Typically -200V is adequate in
a clean system in PPB mode.
Corner lens
Sharp
Sharp
-1600 to 0
Increases and decreases in
value with extraction lens #3
Entrance lens
Sharp
Moderate
-10 to +10
Use this to fine tune the
sensitivity. It has no effect on
the entrance plate voltage
setting
Fringe bias
Sharp
Sharp
-10 to +10
Typically -1V to -3V applied to
the fringe rods will be
sufficient in PPQ mode.
Increasing the negative
voltage usually reduces the
sensitivity. If a voltage more
negative than -4V is required
suspect contamination on the
fringe rods.
The response becomes more
sharp in PPB mode and
typically a -1V setting is
adequate in a clean system.
Entrance plate
Moderate
Moderate
-200 to 0
Use this to fine tune the
sensitivity. It has no effect on
the entrance lens voltage
setting.
Mirror left segment
Sharp
Sharp
0 to +400
Setting is typically within 100V
of the right and bottom mirror
voltages.
When in PPB mode the voltage
setting is typically half of that
used in PPQ mode; however,
the difference in voltage
between the mirror segments
is still uniform but perhaps
closer to 50V.
Mirror right segment
Sharp
Sharp
0 to +400
Setting is typically within 100V
of the left and bottom mirror
voltages