Agilent Technologies 5975T LTM GC/MSD, Troubleshooting And Maintenance Manual

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208 Troubleshooting and Maintenance Guide
13
Analyzer
AMU gain
AMU gain (AmuGain) affects the ratio of DC voltage to RF
frequency on the mass filter. This controls the widths of the
mass peaks.
• Higher gain yields narrower peaks.
• AMU gain affects peaks at high masses more than peaks at
low masses.
AMU offset
AMU offset (AmuOffs) also affects the ratio of DC voltage to RF
frequency on the mass filter.
• Higher offset yields narrower peaks.
• AMU offset generally affects peak widths equally at all
masses.
219 width
m/z 219 is a prominent ion near the middle of the mass range of
PFTBA. The width parameter (Wid219) makes small corrections
to the
m/z 219 peak width. Amu gain and amu offset must be
readjusted after the 219 width is changed. If you are tuning with
a compound other than PFTBA, there may not be an ion at
m/z 219. In that case, set the 219 width to the last value found
for it by Autotune or set it to 0.
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 particular 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.
C A U T I O N
Using the nonpreferred DC polarity may result in very poor
performance. Always use the factory-specified polarity.