In this ppt detailed explanation of the atomic absorption spectroscopy principal,its instrumentation and application.

1. Atomic Absorption Spectroscopy (AAS)

2. Content:
• Introductions
• Principal of AAS
• Its Instrumentation &
• Application

3. Introduction
• Atomic Absorption Spectroscopy
developed by Alan Walsh in the mid
1950s
• Various categories of samples can be
analysed for their elemental composition.
• Concentration up to ppm (parts per
million) can be determined.

4. • In analytical chemistry, Atomic absorption
spectroscopy (AAS) is a technique for
determining the concentration of a particular
metal element (e.g. Fe, Cu, Al, Pb, Ca, Zn)in a
sample ( water, medicine, food) .
• Atomic absorption spectroscopy can be used
to analyze the concentration of over 62
different metals in a solution.

5. Principal
• The technique uses basically the principle that free atoms
(gas) generated in an atomizer can absorb radiation at
specific frequency.
• Atomic-absorption spectroscopy quantifies the
absorption of ground state atoms in the gaseous state .
• The atoms absorb ultraviolet or visible light and make
transitions to higher electronic energy levels. The analyte
concentration is determined from the amount of
absorption.

6. • An “absorption spectrum” is the absorption of
light as a function of wavelength.
• The spectrum of an atom depends on its
energy level structure.
• Absorption spectra are useful for
determination of elements.

7. Instrumentation
• Hollow Cathode Lamp are the most common radiation
source in AAS.
• It contains a tungsten anode and a hollow cylindrical
cathode made of the element to be determined.
• These are sealed in a glass tube filled with an inert gas
(neon or argon ) .
• Each element has its own unique lamp which must be
used for that analysis .
Radiation source
HCL

8. • When a dc voltage of 300–500 V is put across the
anode and cathode,the atoms of the inert gas
undergo ionisation and rapidly attracted by the
cathode.
• The fast moving ions strike the surface of the
cathode and physically displace the surface metal
atoms of the cathode and produce an atomic cloud.
This process called sputtering.
• A portions of the sputtering metal atoms are in
exited states.

9. • They emit their characteristics radiation as
they return to the ground state.
• Eventually,the metal atoms diffuse back to
the cathode surface or to the glass walls of
tube and are redeposited.

10. Nebulizer:
It creates a fine spray of the sample in which the sample,
fuel & oxidant are mixed thoroughly for the introducing
the same into the flame.
Automizer
Flame automizer : This sample solution is first nebulized.
Then,the derosol containing only the droplets of the
appropriate size is projected on the flame where the solvent
get vapourized and finally dissociated to give free atoms
( Ground state).

11. • Intense beam of the analytical light ( radiation) For the
element of interest which is passed through the free
atoms originating from the automizer.
• The wavelength of the light corresponds to the amount
of energy required to excite an electron from the
ground .

12. Monochromator:
In monochromator scattered light of undesirable wave lengths
are removed and only the photons of analytical light line of
desired wave length passing through the flame are isolated.
As a result only a narrow spectral line impinges on the detector
( photomultiplier tube ).
Detecter— photomultiplier tube (PMT):
PMT determine the intensity of Photon of the analytical light
line coming out from the monochromator.
The detector records that reduction as absorption. That absorption is
shown on output device by the data system

14. • Estimation of trace elements in biological fluid like
blood, urine, etc.
• Estimation of trace elements like Copper, Nickle and
Zinc in food products.
• Estimation of Magnesium, Zinc in blood.
• Estimation of Zinc in Zinc insulin solution.
• Estimation of Lead in Calcium carbonate and petrol.
• Estimation of elements in soil samples, water supply,
effluents, ceramics, etc.
Application

15. Referance:
Techniques and methods in biology by K.L. Ghatak
Instrumental methods of chemical analysis by Gurdeep R. Chatwal and K.
anand
https://en.m.wikipedia.org/wiki/Atomic_absorption_spectroscopy