Page 132 - An Introduction to Analytical Atomic Spectrometry - L. Ebdon
P. 132
Page 116
Figure 5.1
Schematic diagram of a commercial inductively coupled plasma mass spectrometer.
nebulizer, spray chamber and torches used for ICP-AES can also be used successfully with ICP-MS.
Hence, liquid sample introduction systems for ICP-MS have between only 1 and 15% efficiency, in
common with those used for ICP-AES.
Once in the ICP, the aerosol droplets are successively desolvated, decomposed and ionized by the high
temperature of the plasma, and it is at this point that the techniques of ICP-AES and ICP-MS diverge.
5.2 Ionization
If an electron absorbs sufficient energy, equal to its first ionization energy, it escapes the atomic
nucleus and an ion is formed. In the ICP the major mechanism by which ionization occurs is thermal
ionization. When a system is in thermal equilibrium, the degree of ionization of an atom is given by
the Saha equation:
where n i, n and n are the number densities of the ions, free electrons and atoms, respectively, Z and Z
a
i
e
a
are the ionic and atomic partition functions,
