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control the pressure to the required limits. The pressure regulator and valves are usually solenoid
operated, so that they can be automatically actuated by the mass spectrometer control-computer.
Consequently, it is easy to rapidly change from electron impact ionization to chemical ionization, if so
desired. In GC/MS tandem systems both forms of sample ionization are commonly used. The sampling
procedure is relatively simple as the sample enters the mass spectrometer as a vapor, in a gas stream,
directly from the concentrator (if one is used) or from the column.
The Inductively Coupled Plasma Mass Spectrometer Ion Source
The inductively coupled plasma (ICP) mass spectrometer ion source evolved from the ICP atomic
emission spectrometer, and is probably more commonly employed in LC/MS than GC/MS. However, it
is occasionally employed in GC/MS, usually in the assays of organometallic materials and in metal
speciation analyses, and so the ion source will be described in this chapter.
Figure 5.8
The ICP Mass Spectrometer Ion Source
