1.
Mrs Vandana Sharma
Assistant Proffesor

2.
 Principle
 Interferences
 Instrumentation
 Applications

3.
 Describe the principle, instrumentation and applications of
following:
 AAS
 Nepheloturbidometry.- 10
 Short note on- various interference in AAS. How they are
corrected.-8
 Explain the difference between Atomic absorption spectroscopy
and flame photometry. 8
 Discuss various types of interferences involved in atomic
absorption spectroscopy. 8
 What is the principle of AAS and explain briefly its
instrumentation. 8
 Explain the theory, applications and instrumentation of Atomic
absorption spectroscopy.-16

4.
 Allan walsh in 1955- Introduced AAS
 Used for quantitative determination of trace metals in liquids of
completely of different nature for example
 Ca+2, Mg+2, Na+, and K+ = ions in blood serum
 Ni+2 ions = in edible oils
 Cu+ ions = in beer sample
 Pb+2 ions = in gasoline (petrol)
 Se+4 ions= in Urine etc
 Ca+2, Mg+2, Na+ ions = in hard water
 sodium and potassium, = in alkali drinking water
 calcium, = in our bones
 It can measure from ppm to ppb.
 These are units indicating concentration, similar to percent.
 In ppm- 'm' stand for million and ppb- 'b' stand for billion.
 1% means 1/100, ppm means 1/million and ppb means 1/billion.
To illustrate simply, 1% would mean one person in 100 people,
 while 1 ppm would be one person in one million people.

5.
 AAS accomplished either
 by using a flame, whereby the sample solution is aspirated
directly into a flame or
 by using an electrothermal device, where by the sample solution
is first evaporated and then ignited on a hot surface.
 Advantage-
 AAS facilitates the estimation of a particular element in the
presence of many other element from the rest
Means
 There is no necessity to separate the test element from the rest,
thereby not only saving a great deal of time but also eliminating
the possibility of various sources of error incurred by these
process.
 In addition AAS may be used for estimation of both aqueous and
nonaqueous solutions

6.
 Atomic absorption spectroscopy involves the study of the
absorption of radiation by neutral atom in gaseous state.
 For this the sample is first converted into atomic vapour and
then absorption of atomic vapour is measured at the selected
wavelength which is characteristic of each element under study.
 For quantitative studies
 the measured absorption ά the concentration of element in
vapour state.
 Since, the techniques involves spraying of a solution into a
flame, it is also called atomic flame Photometry
 This technique appears similar to flame photometry.
 Difference between AAS and flame photometry- AAS is based
on the absorption from the flame rather than emission into the
flame.
 In the technique of atomic absorption, the solution of sample in
a suitable solvent is--- sprayed in a form of fine mist--- into a
flame
 Due to high temperature of flame, the element to be
determined is reduced to element state in a vapour form.

7.
 A suitable source of radiation ---is allowed to fall and pass
through flame to the detector.
 Absorption of energy occurs by the vapour phase of element in
flame and remainder is transmitted to the detector.
 The flame not only serves to convert element into its gaseous
atomic form but also act as a cell in usual type of
spectrophotometer.
 In the absorption process by the gaseous atomic form, a series of
well defined lines occurs due to electronic transition of outer
most shell electrons of the element.
 In the absorption process the number of atoms capable of
absorbing any transmitted light of characteristic wavelength of
ά [concentration of atoms in flame X path length in flame].
 In most determinations,
concentration of sample solution,
wavelength of radiation used for absorption studies,
the temperature and height of flame
is so adjusted to give accurate and quantitative results

8.
 Atomic emission spectroscopy
 Atomic absorption spectroscopy
 Atomic fluorescence spectroscopy

9.
 The basic principles of AAS can be expressed as follows.
 Firstly, all atoms or ions can absorb light at specific, unique
wavelengths.
 When a sample containing copper (Cu) and nickel (Ni), for
example, is exposed to light at the characteristic wavelength of
Cu, then only the Cu atoms or ions will absorb this light.
 The amount of light absorbed at this wavelength ά to the
concentration of the absorbing ions or atoms.
 The electrons within an atom exist at various energy levels.
 When the atom is exposed to its own unique wavelength,--- it
can absorb the energy (photons) and ---electrons move from a
ground state to excited states.
 The radiant energy absorbed by the electrons is directly related
to the transition that occurs during this process.
 Furthermore, since the electronic structure of every element is
unique, the radiation absorbed represents a unique property of
each individual element and it can be measured.

10.
 The amount of light absorbed can be determined as:
 Total amount of light absorbed (at ‫ט‬ ) = (Πe2/mc) * Nf
 ‫=ט‬ Frequency of the light path
 e= Charge on the electron
 m= Mass of the electron
 N= Total number of atoms which can absorb at ‫ט‬
 f= Ability for each atom to absorb at ‫ט‬
 Π, e, m and c= Constant K
 Total amount of light absorbed= K x N x f

11.
 The process of atomic absorption is illustrated in next slide
 The ground state atom absorbs light energy of specific
wavelength ---as it enters the excited state
 As the number of atoms in the light path increases,--- the
amount of light absorbed also increases.
 By measuring the amount of light absorbed, ----a quantitative
determination of the amount of analyte can be made.
 Use of special light sources and careful selection of wavelength -
--allow the specific determination of individual elements.
 When the solution of metallic salt is sprayed on the flame, ---the
fine droplets are formed.
 Due to the thermal energy of flame, ---the solvent in the
droplets evaporate,---- leaving a fine residue, ----which are
converted into neutral atoms.
 These neutral atoms absorb radiation of specific wavelength,
emitted by hollow cathode lamp (HCL)
 Very important note-This lamp is filled with the vapour of

12.
element, which gives specific wavelength of radiation.
 For the determination of every element , hallow cathode lamp is
selected, which contains vapour of the element to be analysed.
 Although this appears to be demerit of AAS, specificity can be
achieved only by the use of HCL
 The intensity of light absorbed by neutral atom ά to the
concentration obeys Beer,s law over a wide concentration range.
 The intensity of radiation absorbed by neutral atom ---- is
measured using photometric detectors ( photo tube or
photomultiplier tube)
 Very important note--In AAS, the flame temperature is not
critical, since ----the thermal energy of flame is used just to---
atomise the sample solution into fine droplets,---- to form a fine
residue and later to neutral atoms.
 Very important Note- Excitation of neutral atoms is brought
about only by radiation from hollow cathode lamp and not by the
thermal energy of the flame.

13.
Additional
information to getting more
clear view

14.
a

15.
 An atomic absorption spectrometer uses these basic principles
and applies them in practical quantitative analysis.
 A typical atomic absorption spectrometer consists of four main
components:
 the light source/radiation source- that emits the spectrum of
the element of inetrest
 the atomization system/ absorption cell- in which atoms the
sample are produced (flame, graphites furnance etc
 the monochromator- for light dispersion
 the detection system- which measures the light intensity and
amplified the signal
 A read out device- that show the reading after it has been
processed
 Type AAS
 1. Single beam atomic absorption spectrophotometer
 2. Double beam atomic absorption spectrophotometer

16.
1. Radiation/light source
A. Hollow cathode lamp-For most elements, the hollow cathode
lamp is satisfactory source for atomic absorption.
 In a few cases, however, the quality of analysis is impaired by
limitations of hollow cathode lamp.
 Limitation- The primary cases involve the more volatile elements
where low intensity and short lamp life are a problem.
B. Electrode –less discharge lamp -The Atomic absorption
determination of these elements can be improved with the use of
electrode –less discharge lamp which is a brighter and more
stable source.
 Construction of Hollow Cathode lamp (HCL)
 Consists of a hollow cup containing the element to be
determined (in this case the element is sodium).
 The anode - tungsten wire- containg (+) charge
 The 2 electrodes are housed in a tube contaning an inert gas.
 The lamp window is of quartz, silica, or glass. The exact material
is used depends upon the wavelength to be determine

17.
When a potential is applied between the two electrodes
a current in the milliampere range arises
the inert gas charged (+) at the anode (tungsten wire)
The charged gas (+) is attracted at the high velocity
to the cathode ( - )
The impact with the cathode
vaporise some of the sodium atoms
The vaporised some sodium atom are excited and
return to the ground state
give rise to the Sodium emission spectrum.
Working

18.
Tungsten wire
And Eg- sodium-element
to be determine
Lamp window eg.
Quartz, silica or glass
(+) (-)
The impact with the cathode
vaporise some of the sodium atoms
The vaporised some sodium atom are excited
and
return to the ground state
give rise to the Sodium emission spectrum.

19.
( - )
( + )

20.
 B. Electrode –less discharge lamp
 In a few cases, however, the quality of analysis is impaired by
limitations of hollow cathode lamp.
 Limitation- The primary cases involve the more volatile elements
where low intensity and short lamp life are a problem.
 The Atomic absorption determination of these elements can be
improved with the use of electrode –less discharge lamp . This
lamp is a brighter and more stable source.

21.
A small amount of the metal or salt of the element for which the
source is to be used---is sealed inside a quartz bulb,
which is placed inside a small, self- contained RF generator or
“driver”
When power is applied (1)to the driver
An RF field (2) is created
The coupled energy will vaporise
and excite the atoms inside the bulb
Causing them to emit their characteristic spectrum.
Electrode-less Discharge lamp: Construction
Working

22.
Electrode-less Discharge lamp
(Radio frequency
generator coil)
Note-An accessory power supply is required to operate and EDL
NOTE-“RF generator” radio frequency generators are used for
testing components etc

23.
2. Chopper
 A rotating wheel, Known as chopper, is interposed or set
or situated b/w the hollow cathode lamp and the flame.
 The rotating wheel is interposed to break the steady light from the
lamp into an intermittent or discontinuously or pulsating light
 This gives a pulsating current in the photocell.
 Note- There is also a steady current is caused by light which is
emitted by a flame.
 But only the pulsating (or alternating) current is amplified and
recorded and
 Advantage of chopper-thus, the absorption of light will be measured
without interference from the light emitted by the flame itself

24.
3. Flame atomizers
 Flame is used for converting the liquid sample into the gaseous
state and----- also converting the molecular entities into an
atomic vapour.
 There is two types of burners in common used
 Total consumption burner
 Premixed burner –
 Premixed burner- The sample is nebulized and mixed with the
fuel and oxidant prior to introduction into the flame, with the
used of a series of buffles
 Sample is drawn from the sample container via vacuum created
by rushing the fuel and oxidant (Aspiration)
 Advantage of is the uniformity of flame produced.
 Uses-Premixed burner is very suitable for the atomic absorption
studies of metals of 1A, 1B, and IIB group together with Ga, In,
Ti, Pb, Te, Mn, Ni, and Pd.

25.
Sample or
1 2
3 4

26.
 In this burner, a mixture of the sample (liquid) and premixed
gases (C2H2 +O2) is allowed to enter the base.
 From the base, the gases enter a region, from where unburn
hydrocarbon gaseous mixture [premixed gases (C2H2 +O2)]
and liquid droplets are allowed to enter a region which is of
free heating and about 1mm in thickness.
 In this region, the liquid is evaporated leaving a residue.
 Heating in this region is done by the heat obtained by
conduction and convection and by diffusion of radicals into it
which initiate the combustion.
 After this the sample residue is burnt to produce atoms
 Production of atoms is initiated in one region and is
completed in another region

27.
Total consumption burner
 It consist of inlets for fuel and
oxidants at the base of the apparatus
 Sample is also kept at the base to be
aspirated.
 Acetylene -commonly used as fuel
and air -used oxidant are forced,
under pressure, into the flame
 The sample is drawn into the flame
by aspiration by vacuum created
because of movement of fuel and
oxidant.
 The aspirated sample reaches-- the
burner head with a nebulizing effect.
 This sample is mixed with fuels and
oxidant at the base of the flame.
 Advantage over other is the entire
consumption of sample,
 Limitation
 The resulting flame is turbulent and
not homogeneous
Acetylene
air

28.
5. Monochromator-
 In atomic absorption measurement – the most common
monochromators are Prism and gratings
 Function of monochromator is to select a given absorbing line
from spectral lines emitted from the Hollow cathode lamp
Collimating mirror
Focusing mirror
gratings
Entrance slit
Exit slit

29.
6. Detectors
 Photomultiplier tube-
 For AAS – most suitable detector
 It has good stability if used with a stable power supply
 In photomultiplier tubes- contains a photocathode, a series of
electrodes called dynodes, and an anode.
 The photocathode is fixed to the power supply terminal

30.
Construction and working Photomultiplier tube
In a vacuum tube, A primary Photo-
cathode is fixed which receives
radiation form the sample
8 to 10 dynodes are fixed Each with
increasing potential about 90V.
Near the last dynode is fixed an
anode/ electron collector electrode
A high voltage is maintained
between the cathode and anode
The light received by cathode
releases electrons
which through series of dynodes
produce more electrons
(+)
(-)
e-
Vacuum
(Coming from
sample)
(Electron
collector
electrode)

31.
7. Recorder
 The recorder can receive electrical signals from the detector to
convert them into a readable response.
 In atomic absorption spectroscopy instrumentation, today we
used a computer system with suitable software for recoding
signals coming from the detector.

32.
Difference between AAS and AES

33.
 Advantages
 Today, the atomic absorption spectroscopy technique is the
most powerful tool in analytical chemistry, forensic science,
environmental analysis, and food industries. It is popular for
analysts due to several advantages.
 The most important advantage is the speed of analysis. It can
analyze various samples within a day.
 Secondly, it is possible to determine all elements at
trace concentration.
 Thirdly, it is not always essential to separate the element
before analysis because AAS can be used to determine one
element in presence of another.
 The atomic absorption spectroscopy principle or
instrumentation can be used to analyze sixty-seven metals and
several nonmetals such as phosphorus and boron

34.
Advantages Limitations
Low cost per analysis Cannot detect non-metals
Easy to operate New equipment is quite
expensive
High sensitivity (up to ppb
detection)
More geared towards
analysis of liquids
High accuracy Sample is destroyed
Mostly free from inter-
element interference
Wide applications across
many industries

35.
1. AAS is widely used in metallurgy, alloy and in inorganic analysis
 Almost all important metals have been analysed by this method
 It is an ideal method for analysis of many ores, minerals and
alloys
2. Biological analysis- A number of elements present in biological
sample can be analyzed by atomic absorption method. These
include estimation of Sodium, potassium, lead, zinc, mercury,
cadmium, magnesium and iron.
3. Pharmaceutical analysis : estimation of zinc in insulin
preparations, oils, creams and in calamine, calcium in number of
calcium salts, lead in calcium carbonate and also as impurities in
number of chemical salt have been reported
4. Sodium, potassium, and calcium in saline and ringer solutions
are estimated by this method
5. In petroleum industry, metallic impurities in petrol, lubricating
oils have been determined

36.
6. Analysis of ash for determining the contents of sodium,
potassium, magnesium, calcium and iron is carried out in boiler
deposits
7. In cement industry, estimation of sodium potassium, calcium,
magnesium is carried out to determine the quality of cement
8. AAS find various applications in various industries like
agriculture, soil, forestry, oceanography, fertilizer etc
9. Atomic absorption spectroscopy is used in the assay of
(a) Intraperitonial dialysis fluid (for Calcium, magnesium)
(b) Activated charcoal (for Zinc)
(c ) Cisplatin (for silver)
Brief

37.
 APPLICATIONS OF ATOMIC ABSORPTION SPECTROSCOPY
 Atomic absorption is the most widely used technique for the
determination of metals at trace and ultra-trace levels in a solution.
 It is used to analyze metals in biological fluids such as blood, hair,
and urine.
 Atomic absorption is used to find out the number of various metals
in the environment.
 It is used in pharmaceutical industries for quantitative analysis of
metals in samples for example, in multivitamins tablets.
 Atomic absorption is used to find the concentration of metals (Ca,
Mg, Fe, Si, Al, ) analysis of water.
 Atomic absorption is used to determine the amount of catalyst.
 It is used for the analysis of crude oil, and petroleum.
 Atomic absorption is used for the analysis of soil samples. For
example, minerals inland before cultivation are tested to get
maximum yields.
 It is used for trace element analysis of cosmetics.
 Atomic absorption is used to find the amount of metals such as gold
in rocks.
 It is used to determine the amount of various metals (Mn, Fe, Cu,
Zn) in foodstuff.
 It is used for the analysis of additives (Ba, Ca, Na, Li, Mg) in
lubricating oils and grease.