Abstract

Inductively-coupled plasma optical emission spectrometry (ICP/OES) has become the primary tool of analytical atomic spectrometry over the past two decades.¹ The success of the ICP may be largely attributed to a torch design which permits a droplet spray from a sample solution to be injected along the axis of the plasma, and from the ability of the plasma to evaporate the solvent, dissociate most chemical species, and render highly excited populations of free atoms and atomic ions. Species concentrations are determined by ratioing measured spectral line intensities to those for known "standard" solutions, and/or by adding quantitative "spikes" to the sample. Under normal operating conditions, the viewing zone utilized for chemical analysis is near local thermodynamic equilibrium (LTE), with an excitation temperature of about 6300K and an electron density of about 10¹⁶ cm^-3. The high excitation energy is a mixed blessing, providing high sensitivity for about 70 elements, along with the possibility of spectral interferences from concomitant species. Reasonably high optical dispersion is employed to minimize spectral interferences, and interferences are normally characterized by line profiling and spectral tables.

© 1992 Optical Society of America