Quadrupole Mass Filter - Agilent Technologies 5975C TAD VL MSD Troubleshooting And Maintenance Manual

7
Analyzer

Quadrupole Mass Filter

The mass filter separates ions according to their mass-to-charge ratio (m/z). At
a given time, only ions of a selected mass-to-charge ratio can pass through the
filter to the detector. The mass filter in the MSD is a quadrupole
The quadrupole is a fused-silica (quartz) tube coated with a thin layer of gold.
The four hyperbolic surfaces create the complex electric fields necessary for
mass selection. Opposing segments are connected; adjacent segments are
electrically isolated. One pair has positive voltages applied, the other negative.
A combined direct current (DC) and radio frequency (RF) signal is applied to
the two pairs of segments. The magnitude of the RF voltage determines the
mass-to-charge ratio of the ions that pass through the mass filter and reach
the detector. The ratio of DC-to-RF determines the resolution (widths of the
mass peaks). There are several parameters that control the DC and RF
voltages. All these parameters are set by Autotune, but also can be manually
adjusted in the Edit Parameters window:
• AMU gain (AmuGain)
• AMU offset (AmuOffs)
• 219 width (Wid219)
• DC polarity (DC Pol)
• Mass (axis) gain (MassGain)
• Mass (axis) offset (MassOffs)
208 5975 Series MSD Troubleshooting and Maintenance Manual
(Figure 47).