7 Analyzer
Mass filter
225
DC polarity
The dc polarity (DC Pol) parameter selects the orientation of the direct current
applied to the quadrupole mass filter. The dc polarity that works best for your
MSD is determined at the factory. It is listed on the final test sheet accompanying
your MSD. It is also listed on a label on the cover over the RF coils. This cover can
be viewed by removing the upper MSD cover.
Mass (axis) gain
Mass gain (MassGain) controls the mass assignment, that is, assignment of a partic-
ular peak to the correct m/z value.
• A higher gain yields higher mass assignment.
• Mass gain affects peaks at high masses more than peaks at low masses.
Mass (axis) offset
Mass offset (MassOffs) also controls the mass assignment.
• A higher offset yields higher mass assignment.
• Mass offset generally affects peaks equally at all masses.
&$87,21
Using the non-preferred dc polarity may result in very poor performance. Always use the
factory-specified polarity.
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