Page 114 - An Introduction to Analytical Atomic Spectrometry - L. Ebdon
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Figure 4.12
Common grating mountings used in ICP-AES: (a) Ebert; (b) Czerny-Turner.
an atomic absorption instrument does not offer sufficient resolution, so a 0.75 m monochromator is
common in modern ICP-AES instruments.
Greater resolution can also be achieved by using an echelle grating, which is ruled with step-shaped
rulings a few hundred times wider than the average wavelength to be studied (i.e. typically 100 lines per
millimetre), in contrast to the general arrangement where the line spacing is similar to the average
wavelength. The grooves have large blaze angles, which results in large angles of diffraction. However,
the echelle is used at orders of 100 or more, and is thus capable of considerable dispersion. The general
arrangement is shown in Fig. 4.13 where the prism, or other dispersing element, is used as an order
