Page 10 - AAS & AES & FES 01082016_Neat

Schematic presentation for components of AAS

Electromagnetic radiation is emitted from a source at the required wavelength in the
ultraviolet· visible region and is directed through a cell that contains atom of the sample.

The sample, usually in solution form, is introduced into the atomizer by some type of
introduction device. The atomizer converts the sample to gas phase ground state atoms that

can absorb the incident radiation.

Absorption of some of the radiation take place in the cell.
The unabsorbed radiation passes through a monochromator and into a transducer (detector)

that transforms the electromagnetic radiation into an electric signal.
The e1ectric signal is amplified, if necessary, and sent to a read out device which provides

the analyst with a percent transmittance, absorbance: or concentration reading.

COMPONENTS OF AAS INSTRUMENT

I.3.1. EMR SOURCES FOR AAS:
The major categories of EMR sources that are used for AAS are continuous sources and

line sources.

I.3.1.1 CONTINUOUS SOURCES
Continuous sources are those that emit broad bands of radiation from which radiation of

the desired wavelength is selected with a monochromator. A relatively popular continuous
source that is used for AAS is the xenon-arc lamp. Electricity is arced between two electrodes in

an envelope that contains xenon at a reduced pressure. The electric energy causes excitation of
the xenon within the lamp. When the xenon atoms and ions return to lower energetic levels,

radiation is continuously emitted over the wavelength range from approximately 200 to 700 nm.

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