Page 157 - An Introduction to Analytical Atomic Spectrometry - L. Ebdon
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Figure 6.4
Non-dispersive AFS system (with permission from PS Analytical Ltd).
This preconcentration method can also be applied to improve the detection limits when aqueous
solutions (or dissolved solid samples) are analysed.
6.4.2 Electrothermal Atomizer
Electrothermal atomizers are also suitable for AFS as, when an inert gas atmosphere is used, quenching
will be minimized. In the nuclear, electronic, semiconductor and biomedical industries where detection
limits have to be pushed as low as 1 part in 10 (or 0.1 pg g in the original sample), electrothermal
13
-l
atomization with a laser as excitation source (LIF-ETA) may be used. Figure 6.5 shows schematically a
common way of observing the fluorescence in LIF-ETA. The fluorescence signal can be efficiently
collected by the combination of a plane mirror, with a hole at its centre to allow excitation by the laser,
positioned at 45° with respect to the longitudinal axis of the tube and a lens chosen to focus the central
part of the tube into the entrance slit of the fluorescence monochromator.
Q. Which type of AFS is of greatest practical use?
Q. Can sensitivity be improved by increasing the intensity of the source in (i) AAS and (ii) AFS?
