Modern pharmaceutical analytical technology

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