Atomic absorption spectroscopy is an analytical technique that measures the concentration of elements by detecting the amount of light absorbed by atoms in the gaseous state at specific wavelengths. It works by vaporizing and atomizing samples using a flame or graphite furnace, then measuring the absorption of light from a hollow cathode lamp at characteristic wavelengths. The instrument consists of a light source, atomizer, monochromator, detector, and readout system. Calibration curves of concentration versus absorption are used to determine unknown concentrations in samples. Potential interferences can affect the analysis and must be minimized. Atomic absorption spectroscopy has various applications in fields like metallurgy, pharmaceutical analysis, and biochemical analysis.

1. ATOMIC ABSORPTION SPECTROSCOPY
GUIDED BY
Dr. S. S. PAWAR
PREPARED BY
VINAYAK R BODHANKAR
M PHARM (SEM-I)
P’CEUTICAL QUALITYASSURANCE
ROLL NO. : 01
Sanjivani College of Pharmaceutical Education &
Research, Kopargaon

2. CONTENTS
 Introduction
 History
 Principle
 Instrumentation
 Interferences
 Applications

3. INTRODUCTION
 Atomic Absorption Spectroscopy is a very common
technique for detecting metals and metalloids in
samples.
 It is very reliable and simple to use.
 It also measures the concentration of metals in the
sample.
 Atomic Absorption Spectroscopy is an analytical
technique that measures the concentration of an
element by measuring the amount of light that is
absorbed at a characteristic wavelength when it
passes through cloud of atoms
 As the number of atoms in the light path increases, the
amount of light absorbed increases.

4. HISTORY OF ATOMIC ABSORPTION
SPECTROSCOPY
 The Atomic Absorption Spectroscopy was first used
as analytical technique in the second half of 19th
century by Robert Bunsen and Robert Kirchhoff.
 The modern form of Atomic Absorption
Spectroscopy was largely developed during the
1950s by a team of Australian chemists.
 They were led by Sir Alan Walsh at the Common
wealth Scientific and Industrial Research
Organization (CSIRO)

5. PRINCIPLE OF ATOMIC ABSORPTION
SPECTROSCOPY
 The technique uses basically the principle that free
atoms 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 & make
transition to higher electronic energy level. The
analyte concentration is determined from the amount
of absorption.
 Concentration measurements are usually determined
from a working curve after the instrument with
standards of known concentration.

6. INSTRUMENTATION
 Parts of Atomic Absorption Spectrophotometer :
 Light source
 Nebulizer
 Atomizer
 Monochromator
 Detector and amplifier
 Read out system

7. Schematic diagram of Atomic Absorption
Spectrophotometer

8. LIGHT SOURCE
 Hollow cathode lamp are the most common radiation
source in AAS.
 It contains a tungsten anode and a hollow cylindrical
cathode .
 These are sealed in a glass tube filled with an inert gas.
(mainly neon or argon)
 Each elements has its own unique lamp which must be
used for that analysis

9. NEBULIZER
 Nebulizer suck up liquid samples at controlled rate.
 Create a fine aerosol spray for introduction into the flame.
 Mix the aerosol and fuel and oxidant thoroughly for
introduction into flame.

10. ATOMIZER
 Elements to be analysed needs to in atomic state and
this is done by means of atomizer.
 Atomization is separation of particles into individual
molecules and breaking molecules into atoms.
 This is done by exposing the analyte to high temperature
in a flame or graphite furnace.
 The atomizers most commonly used nowadays are
(spectroscopic) flames and electrothermal (graphite tube)
atomizers.

11. FLAME ATOMIZATION
 Nebulizer suck up liquid sample at controlled rate and
creates a fine aerosol spray for introduction into flame.
 To create flame, we need to mix an oxidant gas and a
fuel gas.
 In most of the cases air – acetylene flame or nitrous
oxide acetylene flame is used.
 Liquids or dissolved samples are typically used with
flame atomizer.
 Steps in flame atomization :

12. ELECTRO THERMAL ATOMIZATION
 It uses a graphite coated furnace to vaporize the sample.
 Samples are deposited in a small graphite coated tube
which then heated to vaporize and atomize the analyte.
 The graphite tubes are heated using a high current power
supply.
 Steps in electro thermal atomization : Drying
Pyrolysis
Atomization
Cleaning

13. MONOCHROMATOR
 This is very important part in an AAS.
 It is used to separate out all of the thousand of
lines.
 A monochromator is used to select the specific
wavelength of light which is absorbed by the
sample and to remove other wavelengths.
 The selection of the specific light allows the
determination of the selected element in the
presence of others.

14. DETECTOR AND AMPLIFIER
 The light selected by the monochromator is directed onto
a detector whose function is convert the light signal into
an electrical signal.
 Photomultiplier tube detector is mainly used.
 The processing of electrical signal is fulfilled by a signal
amplifier.
 The amplified signal is then displayed on read out system
or fed into a data station for printout by the requested
format.

15. CALIBRATION CURVE
 A calibration curve is used to determine the unknown
concentration of an element in a sample.
 The instrument is calibrated using several solutions of
known concentrations.
 The absorbance of each known solution is measured &
then a calibration curve of concentrations vs absorbance
is plotted.
 The sample solution is fed into instrument & the
absorbance of the element in the solution is measured.
 The unknown concentration of element is then calculated
from the calibration curve.

16. INTERFERENCES IN ATOMIC ABSORPTION
SPECTROSCOPY
 Interference is a phenomenon that leads to change in
intensity of analyte signal in spectroscopy.
 Interferences in AAS fall into two basic categories :
1. Non-Spectral Interferences
affect the formation of analyte items.
2. Spectral Interferences :
high light absorption due to presence of
absorbing species
- Matrix interference
- Chemical interference
- Ionization interfernce

17. NON-SPECTRAL INTERFERENCES
 Matrix interferences :
 When a sample is more viscous or has different surface tension
than the standard it result in difference in sample uptake rate due
to changes in nebulization efficiency.
 Such interferences are minimized by matching the matrix
composition of standard and sample
 Chemical interferences :
 If a sample contains a species which forms a thermally stable
compound with analyte that is not completely decomposed by the
flame energy then chemical interferences exist.
 Such interferences are minimized by using higher flame temp. to
provide higher dissociation energy.

18. IONIZATION INTERFERENCE
 It is more common in hot flames.
 The dissociation process doesn’t stop at formation of
ground state atoms.
 Excess energy of the flame lead to excitation of ground
state atoms to ionic state by loss of electrons thereby
resulting in depletion of ground state atoms.
 Ionization interference is eliminated by an excess of an
element which is easily ionized thereby creating a large
number of electrons in the flame & suppressing the
ionization of the analyte.

19. SPECTRAL INTERFERENCES
 Spectral interferences are caused by presence of another
atomic absorption line or a molecular absorbance band
close to the spectral line of element of interest.
 Most of these interferences are due to molecular
emission from oxides of other element is a sample.

20. APPLICATIONS OF ATOMIC ABSORPTION
SPECTROSCOPY
 Determination of small amount of metals (lead,
mercury, calcium, magnesium)
 AAS is widely used in metallurgy, alloys and in
inorganic analysis.
 Biochemical Analysis : A number of elements
present in biological samples can be analysed by
AAS. These include estimated of sodium, calcium,
potassium, zinc, iron, lead, mercury, etc.
 Pharmaceutical Analysis : Estimation of zinc in
insulin preparation, calcium in calcium salt is done
by using AAS.

21. • Sodium, potassium, calcium in saline and ringer
solution are estimated by AAS.
• Analysis of ash for determining the content of sodium,
potassium, calcium, magnesium and iron is done by
AAS.
• Atomic absorption spectroscopy is used in assay of
a) Intraperitoneal dialysis of fluid for calcium &
magnesium.
b) Activated charcoal for zinc.
c) Cisplastin for liver.

22. References :
• Pharmaceutical analysis Instrumental methods
Volume II by Dr. A.V. Kasture, Dr. S.G. Wadodkar,
Nirali prakashan page no. 23.9 - 23.12
• Instrumental methods of Chemical analysis by
G.R. Chatwal, S.K. Anand, Himalaya publishing
house, fifth edition page no. 2.340 - 2.360

23. THANK YOU