This document provides an overview of atomic absorption spectroscopy (AAS). It describes that AAS involves using a hollow cathode lamp radiation source, a flame to atomize liquid samples, and a monochromator and detector to measure absorption of radiation by metal atoms. The document lists the typical components of an AAS system and explains the working mechanism where liquid samples are nebulized, enter the flame and form free atoms that can absorb radiation. Applications of AAS include analyzing metals in clinical, environmental, and industrial samples.

1. Prepared By,
R Sharmila

2. CONTENTS:
 About instrumentation
 Principle
 Components
 Working mechanism
 Applications of AAS

3. ABOUT INSTRUMENTATION:
 It was discovered by Alan Walsh in the middle of
1950s.
 It is most powerful technique for the determination of
trace metals in the sample.
 It provides the total metal content of sample.
 AAS is independent of molecular form.

4.  Principle of this instrument is similar to other
spectroscopy absorption methods.
 Light of certain wavelength , is able to emit the
spectral lines.
 The sample is aspirated into the flame,.
 Before it enters the flame, the solution gets dispersed
into a mist of very small droplets, which evaporate into
flame, first in gives salt and then vaporizes.
 The flame possesses free unexcited atoms which are
capable of absorb radiation.

5. COMPONENTS:
 Radiation source
 Chopper
 Production of the atomic vapour
 Monochromator
 Detector
 Amplifier

6. RADIATION SOURCE:
 Radiation source for absorption spectrophotometer
should emit stable, intense radiation of the element to be
determined.
 A hollow cathode lamp is used as the radiation source.
 The lamps are useful for the alkali metals, zinc, cadmium,
mercury.

7. CHOPPER:
 A rotating wheel is placed between the hollow
cathode lamp and the flame.
PRODUCTION OF THE ATOMIC VAPOUR:
 Before the liquid sample enters the burner, it is first
converted into small droplets.
 This method of formation of small droplets from the
liquid sample is called nebulization.

8. MONOCHROMATORS:
 Function of the monochromatic is to select a given
absorption line from spectral line emitted from the
hollow cathode.
 Prism of gratings are most commonly used as
monochromators to select a particular wavelength of
light.

9. DETECTORS:
 For AAS, the photomultiplier tube is most suitable.
 In the photomultiplier tube, there is an evacuated envelope,
it contains a photocathode, a series of electrodes called
dynodes and an anode.
AMPLIFIER:
 Electric current from the photomultiplier detector is fed to
the amplifier, it amplifies the electric current.

10. READ OUT DEVICE:
 In AAS, chart recorders are used as read out devices.
 In some AAS, digital read out devices are also used.

11. WORKING MECHANISM:

12. APPLICATION:
 It is used in the branch of science including analytical
chemistry, ceramics, biochemistry.
 It is widely used in clinical laboratories.
 It is used to check petrol, to identify the lead
concentration.
 It is used to identify the element determination in
soil.

13. REFERENCE:
Bioinstrumentation-L Veerakumari
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