Page 113 - Tandem Techniques
P. 113
Page 94
modification to the normal electron impact source is required and a conduit for supplying the reagent
gas is all that is necessary.
The Quadrupole Mass Spectrometer
The most popular mass spectrometer used in tandem systems is the quadrupole mass spectrometer,
either as a single quadrupole or as a triple quadrupole which can provide MS/MS spectra (at technique
that will be discussed later. A diagram of a Quadrupole mass spectrometer is shown in Figure 2.31.
Figure 2.31
The Quadrupole Mass Spectrometer.
The operation of the quadrupole mass spectrometer is quite different from that of the sector instrument.
The quadrupole spectrometer consists of four rods which must be precisely straight and parallel and so
arranged that the beam of ions is directed axially between them. Ideally the rods should be hyperbolic in
cross section but in practice less expensive cylindrical rods are nearly as satisfactory. A voltage
comprising a DC component (U) and a radio frequency component ( ) is applied between
adjacent rods, opposite rods being electrically connected, as
