1. 1

2. 2

3. 3

4. In 1802 by Wollaston when he observed the
"Fraunhofer lines" or absorption lines in the
spectrum of the sun.
This principle was only applied in 1954 by an
Australian physicist, Alan Walsh.
The principle states that "Matter absorbs light
at the same wavelength at which it emits
light".
4

5. 5

6. Gaseous
molecules
Solid/Gas
aerosol
Spray
Light LightLight source Detector
Nebulization
Desolvation
Volatilization
6

7. A light beam is passed through the flame,
Radiation is absorbed, transforming the
ground state atoms to an exited state.
7

8. 8

9. 9

10.  Flame atomization
 Plasma source.
 Flame atomizer.
 Electro thermal atomization
 Graphite furnace.
 Specialized atomization procedures
 Glow discharge atomization.
 Hydride atomization.
 Cold vapor Atomization.
10

11.  A solution of a sample is nebulised by a flow of
gaseous oxidant and gaseous fuel.
 The nebulised liquid sample is converted into
spray.
 The spray on desolvation forms gas/solid
aerosol.
 The solid/gas aerosol by volatilization
converted into gaseous molecule.
11

12. Gaseous
molecule
Atoms
Atomic
ions
Dissociation
(reversible)
Ionization
(reversible)
12

13.  The temperatures of 1700°C-2400°C
occur with the various fuels when air is
the oxidant.
 At these temperatures only easily
decomposed sample are atomized, so
oxygen or nitrous oxide must be used as
the oxidant for more refractory samples.
 These oxidants produce temperatures of
2500°C-3100°C with the common fuels.
13

14.  The burning velocities are important
because flames are stable only in certain
range of gas fluorides.
 Where the flow velocity and the burning
velocity are equal, in this region the
flame is stable.
14

15. FUEL OXIDANT TEMPERATURE °c MAX. BURNING
VELOCITY cmˉ¹
Natural gas Air 1700-1900 39-43
Natural gas Oxygen 2700-2800 370-390
Hydrogen Air 2000-2100 300-440
Hydrogen Oxygen 2550-2700 900-1400
Acetylene Air 2100-2400 158-266
Acetylene Oxygen 3050-3150 1100-2480
Acetylene Nitrous oxide 2600-2800 285
15

16.  Region in a flame.
1. Primary combustion
zone.
2. The interzonal area.
3. Secondary
combustion zone.
16

17.  Primary combustion zone:
 The hydrocarbon flame is recognizable by its
blue luminescence arising from the band
emission of C, CH and other radicals.
 The thermal equilibrium is usually not achieved
in this region.
 Therefore this region is rarely used for
spectroscopy.
17

18.  The interzonal area:
 Which is relatively narrow in hydrocarbon
flames and may reach several centimeters in
height in fuel rich acetylene-oxygen or
acetylene-nitrous oxide sources.
 Because free atoms or prevalent in this region,
it is the most widely used part for the flame
spectroscopy.
18

19.  Secondary combustion zone:
 The products of the inner core are converted
to stable molecular oxides that are then
dispersed into the surroundings.
 The flame profile provides useful information about
the processes that go on in the different parts of a
flame.
 Regions of the flame that have similar values for a
variable of interest.
 Some of these variables include temperature,
chemical composition, absorbance and radiant or
fluorescence intensity
19

20.  The maximum
temperature is located in
the flame about 2.5cm
above the primary
combustion zone.
 It is important particularly
for emission methods to
focus the same part of the
flame on the entrance slit
for all calibrations and
analytical measurements
20

21. In this graph we can
observe the
absorption of 3
different atoms viz.,
 Magnesium
 Silver
 Chromium
21

22.  Magnesium
 It exhibits a maximum absorbance at about
the middle of the flame because of the two
opposing effects.
1. The initial increase in absorbance as the
distance from the base increases results from
an increase in number of Mg atoms
produced by the longer exposure to the
heat of the flame.
2. As the secondary combustion zone
approaches oxidation of Mg ions takes
place, because of the oxide particle
formation absorbance decreases.
22

23.  Silver:
 As it is not easily oxidised, so the increase in the
absorbance is observed.
 Chromium:
 Chromium forms very stable oxides, shows a
continuous decrease in absorbance
beginning close to the burner tip.
23

24.  A typical commercial
laminar flow burner that uses a
concentric-tube nebulizer.
 Aerosol mixed with fuel and passes a
series of baffles ( remove all the finest
solution droplet).
 The aerosol oxidant and fuel are burned
in a slotted burner to provide a 5-10cm
high flame.
24

25. 25

26. FUEL AND OXIDANT REAGENT:
• It is important to have a close control on
the flow rate of both oxidant and fuel.
• Fuel and oxidant are combined in a exact
proportions.
• By using double diaphragm pressure
regulators and needle valves, flow rates are
adjusted.
• Rotameter is used to measure the flow
rates.
26

27. PERFORMANCE CHARACTERISTICS OF
FLAME ATOMIZER
• Reproducibility
• There are two primary reasons for the
lower sampling efficiency of the flame.
1. A large portion of the sample flows down the
drain.
2. The residence time of individual atoms in the
optical path of the flame is brief.
27

28.  Electro thermal atomizer which first
appeared on the market in the early 1970s
 It provides enhanced sensitivity, because
entire sample is atomized in a short period.
 Upto a second of time the atom will be in
a optical path.
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29. 29

30. MECHANISM:
• A little is evaporated in low
temperature and then ashed in a
higher temperature in an electrically
heated graphite tube.
• The ash is atomized at 2000-3000°C for
a short period of time.
• The absorption or fluorescence of the
atomic vapour is then measured.
30

31. 31
• It has a cylindrical graphite
tube that opens at both ends
and it has a central hole for
sample introduction.
• The tube is 5cm long and has
a internal diameter of less than
1cm.

32. • The graphite tube is fitted into a pair of
cylindrical graphite electrical contacts located
at the two ends of the tube.
• These contacts are held in a water cooled
metal housing .
32

33. • Two inert gas streams are provided.
1. The external streams prevents outside air
entering.
2. The internal stream flows into the two ends of the
tube and out through the central sample port.
• The graphite furnace is having a platform is
also made of graphite and is located
beneath the sample entrance port.
• The sample is evaporated and ashed on
this platform.
• By increasing the temperature gradually
atomization occurs.
33

34. OUT PUT SIGNAL
Typical output for the
determination of lead from a
2µlt canned orange juice
At a wave length at which
absorbance or fluoroscence occur
s ,the output raises a maximum
after a few seconds of ignition
followed by a rapid decay back to
zero as the atomization products
escape into the surroundings.
The change is rapid enough
(often <1 ) to require a moderately
fast data acquisition system.
Quantitative determinations are
usually based on peak height,
although peak area is also used
34

35. PRFOMANCE CHARECTERISTICS OF AN
ELECTROTHERMAL ATOMIZER :
 It has a high sensitivity.
 Even small volumes can be atomized.
 The sample volumes between 0.5-10µl
are used.
 The electro thermal atomization is the
method of choice when flame or
plasma atomization provides
inadequate detection limit.
35

36.  Glow discharge atomization
 Hydride atomization
 Cold vapour atomization
36

37.  By using this device atomized vapour can be
swept into a absorption measurements
 Sample is positioned on the sample table
 The chamber is evacuated and the argon gas is
injected through the sample surface
 Current flowing from anode to the sample
cathode ionizes the argon
 The ionized argon bombards the surface causing
the sample sputtering
37

38. DIAGRAM OF GLOW
DISCHARGE
ATOMIZATION
ARGON JET
SPUTTERING THE
SAMPLE ATOMS 38

39.  The ionized argon bombards the surface
causing the sample sputtering.
 Where by the atoms are ejected from
the sample cathode into a vapour
phase.
 Then the atoms are passed through the
cell, where the light is passed from the
source to detector.
 This technique is applicable only when
the sample is having electrical
conductivity.
 Eg.. Of samples : Cadmium, Selenium
and Lead.
39

40.  This technique provides a method for
samples containing Arsenic, Tin, Bismuth,
Lead and selenium etc., into an atomizer
as a gas.
Acidified
aqueous
solution of
sample
Aqueous
solution of
sodium
boro
hydride
Volatile
hydride of
sample
40

41. The volatile hydride is swept into the
atomization chamber by an inert gas.
41

42.  This method is applicable to the
determination of mercury because it is
the only metallic element that has an
appreciable vapour pressure at ambient
at temperature.
 The detection of mercury is important
because it has toxic effects.
 The mercury can be estimated at
253.7nm.
42

43. COLD VAPOUR KIT
43
The mercury is converted to
Hg²+ by oxidizing mixture of
nitric acid and sulphuric acid
followed by reduction of Hg²+
with Sncl2
The elemental mercury is then
swept into long absorption tube
by bubbling stream of inert gas

44.  Radiation Source
 Hallow cathode lamp
 Electrodeless discharge lamp
 Slits
 Atomizers
 Monochromators
 Detectors
44

45.  Hallow cathode lamp:
This is most common source for the atomic
absorption measurements.
 Electrodeless discharge lamp:
This is an alternative light source used in AAS.
45

46.  300 V applied between anode (+) and
metal cathode (-)
 Ar ions bombard cathode and sputter
cathode atoms
 Fraction of sputtered atoms excited,
then fluoresce
 Cathode made of metal of interest
(Na, Ca, K, Fe...)
 Different lamp for each element
46

47.  It provides a radiant intensities usually one to two
orders of magnitude.
 It consists of a sealed quartz tube containing a
small amounts of an inert gas (Argon) and a small
quantity of the metal or its salt whose spectrum of
interest.
DIAGRAM OF
ELECTRODE LESS DISCHARGE LAMP 47

48.  The lamp has no electrode but instead is
energized by an field of radio frequency or
micro wave radiation.
 Ionization of argon causes acceleration by the
high frequency component of the field until
they gain sufficient energy to excite the atoms
of the metals whose spectrum will appear.
 Elements like Selenium, Arsenic & Tin, EDLs
exhibit better detection limits the HC lamps.
48

49. Various atomizers are used in AAS.
Type of Atomizers Typical Atomization
Temperature ,°C
Flame 1700-3150
Electro thermal vaporization (ETV) 1200-3000
Inductive coupled argon plasma
(ICP)
4000-6000
Direct current argon plasma (DCP) 4000-6000
Microwave-induced argon plasma
(MIP)
2000-3000
Glow-discharge plasma (GD) Non thermal
Electric arc 4000-5000
Electric spark 40,000
49

50.  All monochromators contain the
following component parts -
-An entrance slit
-A collimating lens
-A dispersing device
(usually a prism or a grating)
-A focusing lens
-An exit slit
50

51.  Diffraction grating
 Transmission grating
51

52.  BARRIER LAYER CELL
52

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54. 54

55. 55

56.  Spectral Interferences
 The two line correction method
 The continuous source correction method
 Background correction based on the Zeeman Effect
 Background correction based on source self reversal
 Chemical Interferences
 Formation of compounds of low volatility
 Dissociation equilibria
 Ionization equilibria
56

57.  Sample Preparation
 Sample introduction by flow injection
 Organic solvents
 Calibration curves
 Standard addition method
57

58. Samples to be analysed are used in the
form of solution.
Aqueous solutions: These may be diluted with
water and sprayed.
Plant and animal tissues: These are ashed by
wet or dry ashing techniques and then a
solution of ash is prepared in HCl.
Metals as well as alloys: These are first dissolved
in acid or alkali and the resulting solution is
diluted with water.
58

59.  In segmented-flow system, samples
were carried through the system to a
detector by a flowing aqueous solutions
that contained closely spaced air
bubbles.
 The purpose of the air bubbles was to
minimize sample dispersion, to promote
mixing of samples and reagents and to
prevent cross-contamination between
successive samples.
59

60.  The air bubble had to be removed prior
to detection using a debubbler or the
effects of the bubbles had to be
removed electronically.
60

61. • The absorbance can increase when the
solution contains the low molecular
weight alcohols, esters or ketones.
• The effects of the organic solvents is
largely attributable to increased
nebulizer efficiency.
• The lower the surface tension of such
solutions results in smaller drop sizes and
a resulting increase in amount of sample
that reaches the flame.
61

62. • The more rapid solvent evaporation
may also contribute to the effect.
• Methyl iso butyl ketone is used in flame
spectroscopy to extract chelates of
metallic ions.
62

63. • The Atomic absorption should follow
Beer’s law with absorbance being
directly proportional to concentration.
• The calibration curves we get are non-
linear.
• So it is counter productive to perform AA
analysis without permanently confirming
the linearity of the instrument response.
63

64. • A calibration curve that covers the
range of concentrations found in the
sample should be prepared periodically.
• It is even better to use two standards
that bracket the analyte concentrate.
• Any deviation off the standard from the
original calibration curve can then be
used to correct the analytical result.
64

65. • This is particularly used for analyting
samples in which the like hood of matrix
effects are substantial.
• This is one of the most common form
involves adding one or more increments of
a standard solution to sample a liquots
containing identical volumes, this process is
often called spiking the sample.
65

66. • Each solution is then diluted to a fixed
volume before measurement.
• Note that when the amount of sample is
limited, standard additions can be
carried out by successive introductions
of increments of the standard to a single
measured volume of un known.
• Measurements are made on the original
sample on the sample plus the standard
after each addition.
66

67. The element is detected by AAS, by the light intensity emitted by
the sample
This is a series of colored lines on a dark background, depending
on the element, at different wavelengths
Each element has a unique spectrum.
67

68. AAS has a various applications in
every branch of chemical analysis.
The technique is already a firmly
established procedures in analytical
chemistry, ceramics, mineralogy, bio-
chemistry, water supplies, metallurgy,
soil analysis.
68

69. 1. QUALITATIVE ANALYSIS
2. QUANTITATIVE ANALYSIS
3. SIMULTANEOUS MULTICOMPONENT
ANALYSIS
4. DETERMINATION OF METALLIC ELEMENTS
IN BIOLOGICAL MATERIALS
5. DETERMINATION OF METALLIC ELEMENTS
IN FOOD INDUSTRY
6. DETERMINATION OF CALCIUM,
MAGNESIUM, SODIUM AND POTASSIUM
IN BLOOD SERUM
7. DETERMINETION IF LEAD IN PETROL
69

70.  SKOOG, Instrumental analysis , Indian
Edition , CENGAGE Learning,2007.
 B.K. SHARMA , Instrumental methods of
chemical analysis, third edition,GOEL
publishing house,2004.
 http://www.shsu.edu/~chm_tgc/sounds/
sound.html
 www.bing.com.
 www.googleimagesearch.com
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