Page 93 - Tandem Techniques
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element. The sample residue subsequently passes to waste. The light emitted is transmitted through a
quartz window, and is then focused by a quartz lens and spherical mirror onto a diffraction grating.
Figure 2.18
The Helium Plasma Atomic Emission Spectrometer
Courtesy of the Hewlett-Packard Corporation
The dispersed light from the grating is then focused by a second mirror onto the diode array. The diode
array can have any number of diodes, but the contemporary instrument manufactured by Hewlett-
Packard has 211, and its position is adjustable. Consequently, different wavelength ranges can be
selected for monitoring, from the full spectrum provided by the grating. The total wavelength range
covered by the instrument is from 170 nm to 800 nm. Each diode element is 61 mm wide and the
entrance slit is 50 mm wide. In tandem operation, the diode array would be scanned continuously
during the development of the chromatogram and the data
