AAS is an analytical technique used to determine how much of certain elements are in a sample. It uses the principle that atoms (and ions) can absorb light at a specific, unique wavelength. When this specific wavelength of light is provided, the energy (light) is absorbed by the atom.

1. Dr. Rachana Choudhary
Department of Microbiology
Shri Shankaracharya Mahavidyalaya Junwani Bhilai
ATOMIC ABSORPTION SPECTROSCOPY

2. CONTENT
• INTRODUCTION
• PRINCIPLE
• INSTRUMENTATION
• ADVANTAGE AND DISADVANTAGE
• APPLICATION
• REFERENCE

3. INTRODUCTION
• A. Walsh in 1955,fisrtly introduced the AAS.
• AAS determines the presence of Metals in liquid
sample.metal include Fe, Cu, Al, Ca, Zn, Cd and
many more.
• AAS is the most powerful instrumental technique
for the quantitative and qualitative determination
of trace metals in liquids.
• AAS is a technique for determining the
concentration of a particular metal element in a
sample.

4. Elements Detectable By AA are Highlighted in Pink

5. PRINCIPLE:-
• The absorption of energy absolutely by ground state atoms while
they are in the gaseous form.
• Calibration Curves: Atomic absorption should follow Beer’s
law with absorbance being directly proportional to concentration.

6. Systematic diagram of AAS

7. Flame
PARTS ARRANGEMENTS OF THE AAS

8. Three Steps are involved in turning a Liquid
Sample into an Atomic gas:--
 Nebulization
 Desolvation
 Volatilization

9. Flame Atomization
There are three types of
particles that exist in the flame:
1) Atoms
2) Ions
3) Molecules

10. INSTRUMENTATION
• RADIATION SOURCE
• CHOPPER
• ATOMIZER
• MONOCHROMATOR
• DETECTOR
• AMPLIFIER
• READOUT DEVICE

11. Hollow Cathode Lamp
Common Radiation source for Atomic Absorption Spectrophotometer should emit
stable, intense radiation of the element to be determined ,usually a resonance line of the
element.
Ionization of the inert gas occurs when a potential on the order of 300 V is applied
across the electrodes, which generates a current of about 5 to 15 mA.
Most of inert gas at high potential.
Source: Skoog, Holler, and Nieman, Principles of Instrumental Analysis, 5th edition, Saunders College Publishing.
 Electron and ionic impact on cathode
 M(s)  M(g)
 M(g)    M*(g)
 M*(g)  M(g)

12. Flame Burner
• Mn+(aq) + anion(aq)  salt(s)
• salt(s)  salt(g)
• salt(g)  atoms (g)
• M*(g)  M(g)

13. MONOCHROMATOR
•Needed to choose one of several
possible emission lines (lemitted)
associated with HCT.
•Since they are usually
reasonably well separated from
the line of interest, it is
straightforward to use a
monochromator to eliminate this
interference.
Chapter 8&9 - 13

14. SINGLE BEAM AAS INSTRUMENT
DISADVANTAGE:-
Low stability

15. DOUBLE BEAM AAS INSTRUMENT
ADVANTAGE:-
There is no effect of lamp drift and there is no change in detector sensitivity with time.
The ratio between the reference and sample signal is then
amplified and fed to the readout, which may be a digital meter or
a signal recorder.

16. ADVANTAGES OF AAS
• Determination of 68 metals and metalloid elements.
• Ability to make ppb determinations on major components of a sample.
• Precision of measurements by flame are better than 1% rsd. There are
few other instrumental methods that offer this precision so easily.
• AA analysis is subject to little interference.
• Most interference that occurs have been well studied and documented.
• Sample preparation is simple.
• Instrument easy to tune and operate.

17. DISADVANTAGES OF AAS
• Limited to specific elements
• Requires skilled operators
• Interference affects accuracy
• Hollow cathode lamp source is needed for each element.
• Expensive element.
• Sample preparation is time-consuming

18. APPLICATION
• Atomic Absorption is in the assay of elements in biological samples
such as blood, plasma, other body fluids such as urine, saliva, milk &
even in the macromolecules.
• AAS is a more sensitive technique & can detect presence of much less
quantities of element with the exception of alkali .
• AAS can detect quantity less than 1 part 10-6 of more than twenty
elements.

19. REFERENCE
Biophysical Chemistry by Upadhyay & Upadhyay Nath. 3rd
edition,2004.
Principles of Instrumental Analysis. By Skoog, Holler, and Neiman.
5th edition,1998.
Instrumental Methods of Analysis B. Shivashankar
Instrumental methods of chemical analysis Gurdeep R. Chatwal,
Sham K. Anand 5th edition.

20. THANK YOU