More importantly, however, the ICP source has been applied to provide a source of ions for mass
spectrometry (vide infra).
Sample Introduction for Plasma Sources
For the majority of applications, the sample is taken into solution and introduced into the plasma as an
aerosol in the argon stream. The sample solution is pumped by a peristaltic pump at a fixed rate and
converted into an aerosol by a nebulizer (see atomic absorption spectrometry). Various designs of
nebulizer are in use, each having strengths and weaknesses. The reader is directed to the more specialist
texts for a detailed consideration of nebulizers. There is an obvious attraction in being able to handle a
solid directly, and sample volatilization methods using electric spark ablation, laser ablation and
electrothermal volatilization have also been developed.
Analytical Measurements
Qualitative analysis may be made by searching the emission spectrum for characteristic elemental lines.
With modern high resolution optics and computer control, the emission spectrum may be readily
examined for the characteristic lines of a wide range of elements (Figure 8.13). Quantitative
measurements are made on the basis of line intensities which are related to the various factors expressed
in equation (8.1). Under constant excitation
Figure 8.13
ICP-AES scan showing the separation of peaks from a number of elements in the
same sample.
(Courtesy of Instruments SA (UK) Ltd)