A brief on Atomic Absorption Spectroscopy including Introduction, Principle, Instrumentation, Application, Advantages and Disadvantages.

1. Atomic Absorption Spectroscopy
Presented by:
Nursad Jahan Sultana

2. Contents
Introduction
Principle
Instrumentation
Applications
Advantages & Disadvantages

3. Introduction
• Atomic Absorption Spectroscopy is a
ubiquitous technique for detecting
metals and metalloids in samples.
• It is very reliable and simple to use.
• It can analyze over 62 elements.
• It also measures the concentration of
metals in the sample.
Fernández B. Atomic Absorption Spectrometry [Internet]. [place unknown]: Elsevier B.V [date unknown] (updated 2019). Available from:
https://www.sciencedirect.com/topics/materials-science/atomic-absorption-spectrometry?fbclid=IwAR3YTVfwojf0Lj5-
QAWAi3I4xQHkLWPecumKwrjK8ksDecka1YZ8Yq5QdjY

4. History
Fernández B. Atomic Absorption Spectrometry [Internet]. [place unknown]: Elsevier B.V [date unknown] (updated 2019). Available from: https://www.sciencedirect.com/topics/materials-
science/atomic-absorption-spectrometry?fbclid=IwAR3YTVfwojf0Lj5-QAWAi3I4xQHkLWPecumKwrjK8ksDecka1YZ8Yq5QdjY

5. Elements detected by AAS are highlighted in pink in
this periodic table
Masaud SM. Atomic Absorption & Atomic Emission Spectroscopy [Image on internet]. 2014. Available from: https://slideplayer.com/slide/5826081/

6. Principle
The technique uses the principle is 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 UV or visible light and make their transitions to higher electronic energy
levels. Then the concentration is determined from the amount of absorption.
It is a reverse process of flame photometry and emission spectrophotometry. The
relationship between atomic absorption and emission is as-
Basically, atomic absorption takes place when unexcited atoms absorb energy and
become excited atoms. Then concentration measurements are usually determined
from a working curve after calibrating the instrument with standards of known
concentration.
Chatten L. G. Pharmaceutical Chemistry: Theory and Application. India: Satish Kumar Jain; 2008. p. 204
e ̄
+ hv
absorption
emission
e ̄
E

7. Different states of an electron Calibration Curve
Chatten L. G. Pharmaceutical Chemistry: Theory and Application. India: Satish Kumar Jain; 2008. p. 216-217

8. Schematic
diagram
of AAS
Vista SP. Use of Humic acid in agriculture [Image on internet]. 2015 Dec. Available from:
https://www.researchgate.net/publication/314502828_Use_of_Humic_acid_in_agriculture

9. Instrumentation
Chatten L. G. Pharmaceutical Chemistry: Theory and Application. India: Satish Kumar Jain; 2008. p. 207-213
AAS
Hollow
cathode
lamp
Nebulizer
Atomizer
Mono-
chromator
Detector

10. Light source
Quartz window
Pyrex body
Anode
Cathode
Cathode
Hollow Cathode Lamp
Chatten L. G. Pharmaceutical Chemistry: Theory and Application. India: Satish Kumar Jain; 2008. p. 207-209
The light source is designed to emit absorption spectrum of a particular element.
As a light source ‘hollow cathode lamp’ or ‘electrodeless lamp’ is used. However,
HCL is most used. It contains a tungsten anode and a hollow cylindrical cathode
made of the element to be determined. These are sealed in a glass tube that is filled
with inert gas (Neon or Argon).

11. Nebulizer It takes in the test solution at a
controlled rate and generate a fine
aerosol spray for introduction into
the flame.
Flame Atomic Absorption Spectroscopy. [Image on internet]. 2017 Nov 22. Available from: http://insidechem.blogspot.com/2017/11/flame-atomic-absorption-spectroscopy.html

12. Atomizer
Since the elements to be analyzed, should be
in atomic state, atomizer is used to separate
the particles into individual molecules and
break the molecules into atoms. This is done
by exposing the analytes to high temperature
in a flame.
There are two types of atomizer, such as
flame atomizer and graphite tube atomizer.
Flame atomizer is most used. To create flame,
we need to mix an oxidant gas and fuel gas.
Flame Atomizer
Chatten L. G. Pharmaceutical Chemistry: Theory and Application. India: Satish Kumar Jain; 2008. p. 212-213

13. Monochromator
It is used to select the specific
wavelength of light that is absorbed
by the sample and to exclude other
wavelengths.
For alkali metals (Na, K etc.), the
spectrum is simple and low-
resolution monochromator is used.
For transition metals, high-
resolution monochromator is used to
prevent the unabsorbed emission
light originating either from cathode
or filler gas, from falling upon the
detector.
Gopi T. Atomic absorption spectrophotometer [Image on Internet]. Singapore: Environment; 2014 Sep 4. Available from:
https://www.slideshare.net/tejasrigopi/atomic-absorption-spectrophotometer-38678151
Monochromator

14. Detector
Detector is used to convert light signal
into electrical signal, proportional to
the light intensity. The light selected
by the monochromator is directed onto
a detector that is typically a
photomultiplier tube. The processing
electrical signal is fulfilled by a signal
amplifier.
The ideal characteristics of a detector
are fast response times and a linear
response over a wide range of
wavelengths with low noise & high
sensitivity.
Chatten L. G. Pharmaceutical Chemistry: Theory and Application. India: Satish Kumar Jain; 2008. p. 210-211

15. Solvents
Classes of solvents used in Atomic Absorption Spectroscopy are-
-Hydrocarbon
-Esters
-Alcohol
Chlorinated hydrocarbons can be used but produced toxic vapors
from them should be properly ventilated.
Chloroform and Carbon tetrachloride should not be used as they
produce phosgene which is a hazardous compound.
Carbon di-sulfide, Ethers or Acetone should not be used as they
have very low flashpoints and can cause fire hazards.
Chatten L. G. Pharmaceutical Chemistry: Theory and Application. India: Satish Kumar Jain; 2008.

16. Calibration Curve
A calibration curve is used to determine the
unknown concentration of an element in a
solution. The instrument is calibrated by using
several solutions of known concentrations. The
absorbance of each known solution is measured
and then a calibration curve of concentration vs.
absorbance is plotted.
Chatten L. G. Pharmaceutical Chemistry: Theory and Application. India: Satish Kumar Jain; 2008. p. 216-218

17. Application
Environmental studies:
drinking water, ocean
water, soil
Food Industry Pharmaceutical
Industry
Fernández B. Atomic Absorption Spectrometry [Internet]. [place unknown]: Elsevier B.V [date unknown] (updated 2019). Available from:
https://www.sciencedirect.com/topics/materials-science/atomic-absorption-spectrometry?fbclid=IwAR3YTVfwojf0Lj5-
QAWAi3I4xQHkLWPecumKwrjK8ksDecka1YZ8Yq5QdjY
Determination of small amounts of metals (lead, mercury, calcium,
magnesium etc.) as follow:

18. Advantages & Disadvantages
Advantages:
1) Inexpensive,
2) High sample throughput,
3) Fast & easy to use,
4) High precision (ppm/ppb can be identified),
5) Does not need metals separation.
Disadvantages:
1) Only solutions can be analyzed,
2) Relatively large sample quantities are required (1-2mL),
3) It does not determine non-metals,
4) Problems with refractory elements,
5) It can determine only one element at a time.
Chatten L. G. Pharmaceutical Chemistry: Theory and Application. India: Satish Kumar Jain; 2008. p. 204-207

19. Thank you