Atomic Emission Spectroscopy (AES):
Principle : This is simply called as ‘Flame Photometry’, and measures the atoms excited by a
flame (temperature range: 2000 – 31000
K) and not by light source as in the atomic
absorption case. After excitation, atoms will readily lose the gained energy and revert back to
the ground state and the emission occurs. It is that emission that actually being measured.
The wavelengths of the emitted light will almost be similar as those that were absorbed in the
atomic absorption, since exactly the same energy transitions occur, except in the order of
reverse! 9
Instrumentation : A simple flame photometer consists of burner, nebulizer, monochromator,
detector and recorder. The following is the simplified figure:
Applications : It is used exclusively in the quantitative determination of metals in solution,
especially alkali and alkaline earth in the given samples. The principle is like that described
for atomic absorption. Qualitative determination is also possible as each element emits its
own characteristic line spectrum.
Disadvantages : Intensity of emission is very sensitive to changes in flame temperature.
Usually, spectral interference and self-absorption are also encountered which affects the
precision of the measurement. Further, a linear plot of absorbance against concentration is
not always obtained.
No comments:
Post a Comment