Atomic absorption spectroscopy ppt

1. PRESENTED BY:KULKARNI TUKAI N.
M.PHARM 1ST YEAR
NANDED PHARMACY COLLEGE.
1
ATOMIC ABSORPTION SPECTROSCOPY
GUIDED BY:DR.M.H.GHANTE
DEPARTMENT OF CHEMISTRY
NANDED PHARMACY COLLEGE.

2. CONTENTS
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INTRODUCTION
PRINCIPLE
INSTRUMENTATION
APPLICATIONS
CONCLUSION
REFERANCES.

3. INTRODUCTION
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 Atomic absorption spectroscopy is an absorption
spectroscopic method where radiation from a source is
absorbed by non-excited atoms in the vapour state.
 Atomic absorption spectroscopy deals with the
absorption of specific wavelength of radiation by
neutral atoms in the ground state.
 Atomic absorption spectroscopy technique was
introduced for analytical purpose by Walsh, Alkemede
and Milatz in 1956.

4. PRINCIPLE
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 The basic principle of atomic absorption
spectroscopy is to analyze the concentration of
metals in solution.
 When a solution of metallic species is introduced
into a flame, it results in formation of droplets.
 Due to thermal energy of the flame, the solvents in
the droplets evaporate, leaving a fine residue that is
converted to neutral atoms.
 These neutral atoms absorbs radiation of specific
wavelength emitted by Hallow cathode lamp and
intensity is measured by using photometric detector.

5. INTRUMENTATION
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 Atomic absorption spectrophotometer is an instrument
that detects the concentration of metals in liquid
samples.
 It consists of following components:
1. Radiation source
2. Chopper
3. Atomizer
4. Monochromators
5. Detectors
6. Read-out device.

6. 6 FIG 1:ATOMIC ABSORPTION SPECTROMETER

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FIG 2: Line diagram of AAS

8. LIGHT SOURCE
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 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 (neon or
argon ) .
 When a potential is applied about
300V between the two electrodes,
causes ionization of the inert gas
and generation of a current of 5 to
10 mA.
 The lamp window is made up of
either quartz, silica or glass.
FIG 3: HALLOW CATHODE LAMP

9. • The another radiation source commonly
used is Electrode-less discharge lamp.
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 It consists of evacuated tube in
which metal of interest is
placed.
 The tube is filled argon gas at
low pressure and tube is sealed.
 The sealed tube is placed in a
microwave discharge cavity
that causes excitation of metals
inside the sealed tube.
FIG 4: ELECTRODE-LESS DISCHARGE LAMP

10. ATOMIZERS
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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.
 In order to achieve absorption of atoms, it is necessary
to reduce the sample into a atomic state.
 This is done by-
a. Flame atomizers
b. Non-flame atomizers.

11. FLAME ATOMIZERS
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 A flame atomizer contains a pneumatic nebulizer,
which converts the sample solution into a mist, or
aerosols.
 In most atomizers, the high pressure gas is the
oxidant, and the aerosol containing oxidant is
subsequently mixed with fuel.
 The burners commonly used in atomic absorption
spectroscopy are laminar and total consumption
burners.

12. CONT…
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 In Total consumption burner, the
sample solution, the fuel, and
oxidizing gases are passed through
separate passages to meet at the
opening of the base of flame.
 Sample in liquid form then the
flame breaks into the droplets which
are evaporated and burns. Leaving
the residue which is reduced to
atoms.
 Total consumption burners do use
oxygen with hydrogen or acetylene,
gives very hot flames.
 The only disadvantage of this burner
is that it is noisy and hard to use.
FIG 5: Total Consumption Burner

13. MONOCHROMATORS
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 The main purpose of the Monochromator is to isolate a
single atomic resonance line (wavelength) from the lines
emitted by the hollow cathode lamp.
 It is an adjustable filter that selects a specific, narrow
region of the spectrum for transmission to the detector.
 A monochromator consists of an entrance slit, a
dispersion device and an exit slit.

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15. DETECTORS
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 The light selected by the monochromator is directed or
passed to a detector whose main function is to convert light
signal into an electric signal.
 For atomic absorption spectroscopy, photomultiplier tube is
the most common detector used.
 In photomultiplier tube, there is an evacuated envelope
which consists of a photocathode, dynodes and an anode.
 Photocathode is fixed to the terminal of power supply and
when voltage is applied to electrodes, the photon hit the
cathode and generates electrons which eventually flow
towards cathode and resultant current is produced.
 The resultant current further goes into an recorder where
the signals are recorded.

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FIG 6: Photomultiplier tube

17. RECORDER
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 In most atomic absorption
measurements, a chart
recorder is used as a read-
out device.
 A chart recorder is a
potentiometer using
servometer to move the
recording pen.
 Digital read-out devices
are also used in some
atomic absorption
measurements.
FIG 7: Recording devices

18. APPLICATIONS
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 Determination of even small amounts of metals
(lead, mercury, calcium, magnesium, etc.)
 Environmental studies: drinking water, ocean water,
soil.
 Food industry.
 Pharmaceutical industry.
 Sodium, potassium and calcium in ringer solutions
are estimated by this method.
 In cement industry, estimation of sodium, potassium,
calcium and magnesium is carried out to determine
the quality of cement.

19. REFERANCES
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 Dr. A. V. Kasture, Dr. G. Wadodkar, A Textbook of
Pharmaceutical Analysis, Nirali Prakashan, 2nd edition,
pp 23.1-23.12
 Douglas A. Skoog, Principles of Instrumental analysis,
6th edition, Cengage Learning Publisher, pp 670-689.
 Gurdeep. R. Chatwal, Instrumental methods of chemical
analysis, Himalaya Publishing House, 6th edition,
pp 2.340-2.366.

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