it is about history, working principle, instrumentation of atomic absorption spectrophotometer.

1. ATOMIC
ABSORPTION
SPECTROSCOPY
PRESENTED BY:- NIDHI SINGH
15SBAS201004
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2. Introduction
• It is very reliable and simple to use
• It can analyze over 62 elements
• It also measures the concentration of metals in sample 2
Atomic absorption spectroscopy is a
quantitative method of analysis of any kind of
sample ; that is applicable to many metals and a
few nonmetals.

3. HISTORY
• The technique was introduced in 1955 by Alan Walsh in
Australia ( 1916 – 1998 ).
• The first commercial atomic absorption spectrometer
was introduced in 1959.
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The application of atomic
absorption spectra to chemical
analysis

4. PRINCIPLE
• The technique uses basically the principle that free
atoms ( gas ) generated in an atomizer can absorb
radiation at specific WAVELENGTH.
• The atoms absorb ultraviolet or visible light and make
transitions to high electronic energy levels. The analyte
concentration is determined from the amount of
absorption.
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5. • Concentration measurements are usually determined
from a working curve after calibrating the instrument
with standards of known concentration.
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6. INSTRUMENTATION
Atomic
Absorption
Spectrometer
Hollow cathode
lamp
Detector
MonochromatorAtomizer
Nebulizer
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8. LIGHT SOURCE
• Hollow Cathode Lamp are 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 . 8

9. Hollow Cathode Lamp
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10. HollowCathode Lampfor Aluminum (Al)
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11. Nebulizer
• suck up liquid samples at controlled rate.
• create a fine aerosol spray.
• Mix the aerosol and fuel and oxidant(AIR
ACYTYLENE, NITROUS OXIDE-ACTYLENE)
thoroughly for introduction into flame.
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12. Sample Atomization Technique
Flame
Atomization
Electro thermal
Atomization
Hydride
Atomization
Cold-Vapor
Atomization
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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 .
Atomization

13. Flame Atomization
• Mix the aerosol and
fuel and oxidant
thoroughly
for introduction into
flame.
• An aerosol is a colloid
of fine solid particles
or liquid droplets, in
air or another gas.
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14. Flame Atomization
sample
mist
Solid/gas
aerosol
Gaseous
molecules
Atoms
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nebulization
disolvation
volatilization
dissociation

15. Disadvantages of Flame Atomization
• Only 5-15% of the nebulized sample reaches the flame.
• A minimum sample volume of 0.5-1.0 ml is needed to
give a reliable reading.
• Samples which are viscous require dilution with a solvent.
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16. Graphite Furnace Atomization
• Uses a graphite coated furnace to vaporize the sample.
• ln GFAAS sample, samples are deposited in a small
graphite coated tube which can then be heated to
vaporize and atomize the analyte.
• The graphite tubes are heated using a high current
power supply.
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17. Graphite Furnace Technique
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18. Advantagesof Graphite Furnace
Technique
• Small sample size
• Very little or no sample preparation is needed
• Sensitivity is enhanced
• Direct analysis of solid samples
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19. Disadvantages of Graphite Furnace
Technique
• Analyte may be lost at the ashing stage.
• The sample may not be completely atomized
• The precision is poor than flame method
• Analytical range is relatively low
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20.  An important use in
determining organic mercury
compounds in samples and
their distribution in the
environment.
 Limited to the determination of mercury, due to it being the only
metallic element to have a large enough vapor pressure at ambient
temperature.
 The method initiates by converting mercury into Hg2+ by
oxidation from nitric and sulfuric acids, followed by a reduction of
Hg2+ with tin(II) chloride. The mercury, is then swept into a long-
pass absorption tube by bubbling a stream of inert gas through the
reaction mixture.
Cold Vapor Atomization

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I nst r ument at i on

23. MONOCHROMATOR
• 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.
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24. DIFFRACTION GRATING
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25. 25

26. • Grating monochromators are located within
compartments of AAS instruments and are
responsible for producing narrow bands of
radiation.
• There are five components found in most grating
monochromators:
• an entrance slit,
• a collimating mirror,
• a reflection grating,
• a focusing element,
• and an exit slit.
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27. 27

28. 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.
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29. 29

30. WORKING
• Hollow cathode lamps are used as a radiation source
which emits the required ray to the sample.
• The nebulizer sucks the sample, mixes it with fuel and
oxidant and forms a fine aerosol – ready to be send to
the atomizer.
• The atomizer transforms the aerosol into vapours (gas)
with the help of a flame.
• The monochromator which is a wavelength selector
allows a narrow range of wavelength to pass through it
and fall on the vapourised sample. 30

31. • As the radiation fall on the vapours/atoms, it absorbs
some of it and some of them are transmitted.
• These transmitted light are further detected by the
detector and the results are displayed on the monitor.
• The light absorbed by the vapours (sample) are
displayed as the result in AAS.
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32. Calibration Curve
• 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 32

33. 33
Interferences in Atomic Absorption
Spectroscopy
• Interference is a phenomena that leads to changes in
intensity of the analyte signal in AA spectroscopy.
Interferences in fall into two basic categories namely,
non- spectral & spectral .
• Non-spectral interferences affect the formation of
analyte items and spectral interferences result in higher
light absorption due to presence of absorbing species
other than the analyte element.

34. Non-spectral interferences
• Matrix interference
• When a sample is more viscous or has different surface
tension than the standard it can result in differences in sample
uptake rate due to changes in nebulization efficiency.
• Such interferences are minimized by matching as closely as
possible the matrix composition of standard and sample
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35. Ionization interference
• Excess energy of the flame can lead to excitation of ground state
atoms to ionic state by loss of electrons thereby resulting in
depletion of ground state atoms.
• In cooler flames such interference is encountered with easily
ionized elements such as alkali metals and alkaline earths.
• Ionisation interference is eliminated by adding an excess of an
element which is easily ionized thereby creating a large number of
free electrons in the flame and suppressing ionization of the
analyte.
• Salts of such elements as K, Rb and Cs are commonly used as
ionization suppressants. 35

36. 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 common spectral interferences are due to molecular
emissions from oxides of other elements in the sample.
• The problem is overcome by measuring and subtracting the
background absorption from the total measured absorption
to determine the true atomic absorption.
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37. Applications
1) Presence of metals as an impurity or in alloys could be done
easily
2) Level of metals could be detected in tissue samples like
Aluminum in blood and Copper in brain tissues
3) 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
4) Determination of elements in the agricultural and food
products
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38. THANK YOU
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