Inner Workings – Triple Quadrupole MS versus Single Quadrupole MS 2
How a single quadrupole mass spectrometer works
Agilent 6400 Series Triple Quad LC/MS Concepts Guide 15
The RF is applied to all four rods, but the negative (–) rods are
180 degrees out of phase with the positive (+) rods. The rods are
labeled + and – in reference to the DC voltages applied to them.
All ions that comprise the sample are generated at the source.
However, when a specific set of voltages is applied, only ions of
the corresponding m/z value may pass through the quadrupole
to reach the detector. As the voltages are increased to other
values, ions with other m/z values are allowed to pass through.
A full MS scan is obtained by increasing the DC and RF voltages
applied to the four rods over an expanded range of values.
How a single quadrupole mass spectrometer works
A diagrammatic model can be used to illustrate the concept of
how a single quadrupole instrument works. See Figure 2.
Figure 2 Conceptual model of a single quadrupole mass spectrometer
In the model,
• All of the ions contained in a sample are formed in the
external ionization source and collected in a funnel. The balls
of different colors and sizes represent different ions having
different m/z values.
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