a brief discussion of AAS, an analytical technique use for heavy metal analysis. Atomic absorption spectroscopy is a quantitative method of analysis of any kind of sample; that is applicable to many metals AAS can be used to determine over 70 different elements in solution, or directly in solid samples via electro thermal vaporization. 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. Applications: Presence of metals as an impurity or in alloys can be perform. Level of metals could be detected in tissue samples like Aluminum in blood and Copper in brain tissues. Due to wear and tear there are different sorts of metals which are given in the lubrication oils which could be determined for the analysis of conditions of machines. Determination of elements in the agricultural samples. Water sample analysis (e.g. Ca, Mg, Fe, Si, Al, Ba content). Food sample analysis. Analysis of animal feedstuffs (e.g. Mn, Fe, Cu, Cr, Se, Zn). Analysis of additives in lubricating oils and greases (Ba, Ca, Na, Li, Zn, Mg). analysis of soils. Clinical sample analysis (blood samples: whole blood, plasma, serum; Ca, Mg, Li, Na, K, Fe). Analysis of Environmental samples such as- drinking water, ocean water, soil. Pharmaceutical sample Analysis: Estimation of zinc in insulin preparation, calcium in calcium salt is done by using AAS. Principle: The sample, in solution, is aspirated as a spray into a chamber, where it is mixed with air and fuel. This mixture passes through baffles, here large drops fall and are drained off. Only fine droplets reach the flame. Light from the hollow-cathode lamp passes through the sample of ground-state atoms in the flame. The amount of light absorbed is proportional to the concentration. The element being determined must be reduced to the elemental state, vaporized, and imposed in the beam of the radiation in the source. When a ground-state atom absorbs light energy, an excited atom is produced. The excited atom then returns to the ground state, emitting light of the same energy as it absorbed. The flame sample thus contains a dynamic population of ground-state and excited atoms, both absorbing and emitting radiant energy. The emitted energy from the flame will go in all directions, and it will be a steady emission. Because the purpose of the instrument is to measure the amount of light absorbed, the light detector must be able to distinguish between the light beam emitted by the hollow cathode lamp and that emitted by excited atoms in the flame.

1. AAS (Atomic Absorption Spectrometry
(AAS)
MRIDU KULWANT
1

2. CONTENTS
 Introduction
 History
 Principle
 Instrumentation
 Application
2

3.  Atomic absorption spectroscopy is a quantitative method of analysis of any kind
of sample; that is applicable to many metals
 AAS can be used to determine over 70 different elements in solution, or
directly in solid samples via electro thermal vaporization.
 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.
 Optical Atomic Spectroscopy/ Optical Spectrometry
 Absorption
 Emission
INTRODUCTION
3

4. ATOMIC EMISSION SPECTROSCOPY
 Examines the wavelengths of photons
emitted by atoms or molecules during
their transition from an excited state to a
lower energy state.
 Each element emits a characteristic set
of discrete wavelengths.
 By observing these wavelengths the
elemental composition of the sample can
be determined.
ATOMIC ABSORPTION SPECTROSCPY
 Measures the loss of electromagnetic
energy after it illuminates the sample
under study.
 The energy in certain amount is
absorbed during transition to the higher
level.
 The amount of energy absorbed gives
estimate of the concentration of the
analyte in the sample.
COMPARISON
4

5. HISTORY
Source: http://www.science.org.au/academy/memoirs/walsh2.htm#1
 The technique was introduced in 1955 by Alan Walsh in Australia (1916-1998).
 The application of atomic absorption spectra to chemical analysis.
 The first commercial atomic absorption spectrometer was introduced in 1959.
5

6.  The sample, in solution, is aspirated as a spray into a chamber, where it is mixed
with air and fuel.
 This mixture passes through baffles, here large drops fall and are drained off. Only
fine droplets reach the flame.
 Light from the hollow-cathode lamp passes through the sample of ground-state
atoms in the flame.
 The amount of light absorbed is proportional to the concentration.
 The element being determined must be reduced to the elemental state, vaporized, and
imposed in the beam of the radiation in the source.
 When a ground-state atom absorbs light energy, an excited atom is produced.
 The excited atom then returns to the ground state, emitting light of the same energy
as it absorbed.
 The flame sample thus contains a dynamic population of ground-state and excited
atoms, both absorbing and emitting radiant energy. The emitted energy from the
flame will go in all directions, and it will be a steady emission.
 Because the purpose of the instrument is to measure the amount of light absorbed,
the light detector must be able to distinguish between the light beam emitted by the
hollow cathode lamp and that emitted by excited atoms in the flame.
PRINCIPLE
6

7. 1) Light source
2) Nebulizer
3) Atomizer
4) Monochromator
5) Detector
INSTRUMENTATION
7

8. Hollow Cathode Lamp (HCL)
 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.
 The invention of hollow cathode lamp by
Walsh in 1955 made practical applications of
AAS possible
1. LIGHT SOURCE
Electrode-less Discharge Lamps (EDL)
 designed to be physically interchangeable with Lumina Hollow Cathode Lamps.
 The benefits of electrode- less discharge lamps are realized especially when
analyzing volatile elements like As, Sb, Bi, Cd, Hg, Rb, Sn, Te, etc. Sputtering of
such metal atoms and their adsorption on cathode lamp side walls and windows
begins to affect the useful life of the lamps.
 Their power supplies are built into all PinAAcle series of atomic absorption
spectrometers. PerkinElmer System 2 EDLs consist of the element, or a salt of the
element, sealed in a quartz bulb containing an inert gas atmosphere. 8

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

10.  Atomization is separation of particles into individual molecules and breaking
molecules into atoms.
 This is done by exposing the analyte to high temperatures in a flame or graphite
furnace.
 Sample Atomization Technique
 Flame Atomization
 Electro thermal Atomization
 Hydride Atomization
 Cold- Vapour Atomization
3. ATOMIZATION
10

11.  Nebulization is process by which sample liquid converts into a fine mist & aerosols.
 Desolvation is a thermodynamically driven, self-assembly process for polymeric
materials to prepare nanoparticles.
 Volatilization is the process of converting a chemical substance from a liquid or solid
state to a gaseous or vapor state.
 Dissociation is process in which molecules (or ionic compounds such as salts, or
complexes) separate or split into other things such as atoms, ions, or radicals, usually
in a reversible manner.
Flame Atomization
 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.
 liquid or dissolved samples are
typically used with flame
atomizer.
11

12.  This is a very important part in an AA spectrometer. It is used to separate out all of
the thousands of lines.
 A Monochromator is used to select the specific wavelength of light which is
absorbed by the sample, and to exclude other wavelengths.
 The selection of the specific light allows the determination of the selected element
in the presence of others.
4. MONOCHROMATOR
12
5. DETECTOR
 The light selected by the Monochromator is directed onto a detector that is
typically a photomultiplier tube, whose function is to convert the light signal into
an electrical signal proportional to the light intensity.
 The processing of electrical signal is fulfilled by a signal amplifier.
 The signal could be displayed for readout, or further fed into a data station for
printout by the requested format.

13.  A calibration curve is used to determine the unknown concentration of an
element in a solution.
 The instrument is calibrated 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.
 The sample solution is fed into the instrument, and the absorbance of the
element in this solution is measured.
 The unknown concentration of the element is then calculated from the
calibration curve.
Calibration Curve
13

14.  Interference is a phenomenon that leads to change in intensity of analyte signal in
spectroscopy.
 Interferences in AAS fall into two basic categories:
 Non-Spectral Interferences affect the formation of analyte items.
 Spectral Interferences
 high light absorption due to presence of absorbing species
 Matrix Interference: 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.
 Chemical interference: 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.
 Ionization Interference: It is more common in hot flames. The dissociation
process doesn't stop at formation of ground state atoms.
 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.
Interferences
14

15. 15
Fig; Schematic diagram of AAS instruments

16.  Presence of metals as an impurity or in alloys can be perform.
 Level of metals could be detected in tissue samples like Aluminum in blood and
Copper in brain tissues.
 Due to wear and tear there are different sorts of metals which are given in the
lubrication oils which could be determined for the analysis of conditions of
machines.
 Determination of elements in the agricultural samples.
 Water sample analysis (e.g. Ca, Mg, Fe, Si, Al, Ba content).
 Food sample analysis.
 Analysis of animal feedstuffs (e.g. Mn, Fe, Cu, Cr, Se, Zn).
 Analysis of additives in lubricating oils and greases (Ba, Ca, Na, Li, Zn, Mg).
analysis of soils.
 Clinical sample analysis (blood samples: whole blood, plasma, serum; Ca, Mg,
Li, Na, K, Fe).
 Analysis of Environmental samples such as- drinking water, ocean water, soil.
 Pharmaceutical sample Analysis: Estimation of zinc in insulin preparation,
calcium in calcium salt is done by using AAS.
APPLICATIONS
16

17. 17
AAS
 https://www.perkinelmer.com/category/atomic-absorption-
spectroscopy-aas
 https://lab-training.com/aas/
 https://en.wikipedia.org/wiki/Atomic_absorption_spectroscopy
 https://www.scimed.co.uk/education/what-is-atomic-absorption-
spectroscopy-aas/
 https://www.slideshare.net/sharmasuriti/atomic-absorption-
spectroscopy-15185397
REFERENCES