Monochromators:

Emission from plasma is usually polychromatic in nature which implies that it consists of a large number of radiations of different wavelengths. More so, the bandwidths of optical emission lines from the plasma are typically of the order of 0.001 nm. These need to be suitably dispersed to analyse for the possible elements in the analyte. Resolution is important because of the complexity of ICP emission spectra, in terms of very large number of individual emission lines observed from samples. If not resolved, it would cause extensive spectral interference. There are three common devices used for the separation or dispersion of light. These are gratings, prisms and Michelson interferometers. In ICP-AES spectrometers, the resolution of the complex spectra is achieved by using ruled grating monochromators having a large number of grooves on the grating. Some instruments on the other hand employ holographic gratings.