Page 95 - Tandem Techniques

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grating by means of a spherical mirror. The diffraction grating is movable, and so it can be set to
monitor a particular wavelength that is characteristic of the element being measured, or it can be
scanned to produce a complete absorption spectrum of the sample.

Figure 2.19
The Flame Atomic Absorption Spectrometer

After leaving the grating, light of a selected wavelength, or range of wavelengths, is focused onto the
photo cell. The position of the diffraction grating determines the wavelength of the light that is to be
monitored. The flame absorption spectrometer is fairly sensitive, and can be readily used as a tandem
instrument combined with a chromatograph, providing that an appropriate interface is employed.

Chiro-Optical Measurements

Over the last decade there has been a growing interest in chiral chromatography, a term given to the
separation of optically active compounds by chromatographic techniques. This interest has arisen
largely as a result of the recognition that the majority of physiologically active substances exist in chiral
form. Furthermore, in many countries, it is now mandatory that if a drug can exist with different chiral
structures,