Atomic absorption spectroscopy involves atomizing a liquid sample and measuring the absorption of light from a lamp that emits light of a specific wavelength corresponding to the element being measured. The technique was introduced in 1955 and involves using a flame or graphite furnace to atomize the sample, a monochromator to select the wavelength of light, and a detector to measure the absorption. Common interferences include overlap of spectral lines, incomplete dissociation of compounds, and physical effects related to viscosity, solvent, and ionization. Atomic absorption spectroscopy is widely used for trace metal analysis in applications such as clinical analysis, environmental monitoring, pharmaceuticals, and mining.
Principle
Interferences
Instrumentation and
Applications
The principle of flame photometer
is based on the measurement of the emitted light intensity when a metal is introduced into the flame.
The wavelength of the colour gives information about the element and
the colour of the flame gives information about the amount of the element present in the sample.
Flame photometry is one of the branches of atomic absorption spectroscopy.
It is also known as flame emission spectroscopy.
Currently, it has become a necessary tool in the field of analytical chemistry. Used to
Determine the concentration of certain metal ions like
potassium,lithium, calcium, cesium etc. In flame photometer spectra the metal ions are used in the form of atoms.
(IUPAC) Committee on Spectroscopic Nomenclature has named this technique as flame atomic emission spectrometry (FAES). Principle of Flame photometer
The compounds of the alkali and alkaline earth metals (Group II) dissociate into atoms when introduced into the flame.
Some of these atoms further get excited to even higher levels. But these atoms are not stable at higher levels.
Hence, these atoms emit radiations when returning back to the ground state.
These radiations generally lie in the visible region of the spectrum.
Each of the alkali and alkaline earth metals has a specific wavelength. Instrumentation-Source of flame, Nebuliser, Monochromator(Prism monochromator, Grating monochromators)DETECTOR (
The radiation emitted by the elements is mostly in the visible region and measured by photo detector. Hence conventional detectors like photo voltaic cell or photo tubes or photomultiplier tube is used), READ OUT DEVICE
[The signal from the detector is shown as a response in the digital read out device. The readings are displayed in an arbitrary scale (% Flame Intensity).], working of flame photometer, Advantages and disadvantage of flame photometer, Errors /interference in Flame Photometry-Flame Temperature, chemical interference, Radiation interference
Application of flame photometry
Principle
Interferences
Instrumentation and
Applications
The principle of flame photometer
is based on the measurement of the emitted light intensity when a metal is introduced into the flame.
The wavelength of the colour gives information about the element and
the colour of the flame gives information about the amount of the element present in the sample.
Flame photometry is one of the branches of atomic absorption spectroscopy.
It is also known as flame emission spectroscopy.
Currently, it has become a necessary tool in the field of analytical chemistry. Used to
Determine the concentration of certain metal ions like
potassium,lithium, calcium, cesium etc. In flame photometer spectra the metal ions are used in the form of atoms.
(IUPAC) Committee on Spectroscopic Nomenclature has named this technique as flame atomic emission spectrometry (FAES). Principle of Flame photometer
The compounds of the alkali and alkaline earth metals (Group II) dissociate into atoms when introduced into the flame.
Some of these atoms further get excited to even higher levels. But these atoms are not stable at higher levels.
Hence, these atoms emit radiations when returning back to the ground state.
These radiations generally lie in the visible region of the spectrum.
Each of the alkali and alkaline earth metals has a specific wavelength. Instrumentation-Source of flame, Nebuliser, Monochromator(Prism monochromator, Grating monochromators)DETECTOR (
The radiation emitted by the elements is mostly in the visible region and measured by photo detector. Hence conventional detectors like photo voltaic cell or photo tubes or photomultiplier tube is used), READ OUT DEVICE
[The signal from the detector is shown as a response in the digital read out device. The readings are displayed in an arbitrary scale (% Flame Intensity).], working of flame photometer, Advantages and disadvantage of flame photometer, Errors /interference in Flame Photometry-Flame Temperature, chemical interference, Radiation interference
Application of flame photometry
Atomic absorption spectroscopy, History, atomization techniques, and instrume...Muhammad Asif Shaheeen
History, principle, types, instrumentation, comparison with atomic emission spectroscopy, interference, advantages and disadvantages of different types of atomization techniques.
In this slide contains Interference In Atomic Absorption Spectroscopy and applications.
Presented by: Shaik Gouse ul azam. ( department of pharmaceutical analysis.)
RIPER, anantpur.
Gas chromatography and its instrumentationArgha Sen
Gas chromatography is an unique technology which helps us in separating volatile analytes. Its is an easy and reproduciple method for detecting residual solvents found in APIs.
Atomic Absorption spectrometer is an instrument used for quantitative analysis of most of the metals in nano grams. This is highly sensitive technique used for analysis.
Atomic absorption spectroscopy, History, atomization techniques, and instrume...Muhammad Asif Shaheeen
History, principle, types, instrumentation, comparison with atomic emission spectroscopy, interference, advantages and disadvantages of different types of atomization techniques.
In this slide contains Interference In Atomic Absorption Spectroscopy and applications.
Presented by: Shaik Gouse ul azam. ( department of pharmaceutical analysis.)
RIPER, anantpur.
Gas chromatography and its instrumentationArgha Sen
Gas chromatography is an unique technology which helps us in separating volatile analytes. Its is an easy and reproduciple method for detecting residual solvents found in APIs.
Atomic Absorption spectrometer is an instrument used for quantitative analysis of most of the metals in nano grams. This is highly sensitive technique used for analysis.
A short lecture about Atomic Spectroscopy: Flame Photometry, Atomic Absorption, and Atomic Emission with Coupled Plasma (FP, AA and ICP-AES). Presented at 28.03.2011, Faculty of Agriculture, Hebrew University of Jerusalem, by Vasiliy Rosen, M.Sc.
introduction
Interference is a phenomena
that leads to changes (either positive or negative) in intensity of the analyte signal in spectroscopy.
Interferences in atomic absorption spectroscopy fall into two basic categories, namely, non-spectral and spectral.
1. spectral 2. Non Spectral ( Matrix interference, chemical interference, ionization interference)
PRINCIPLE - atomic absorpion spectroscopy
Atoms of the analyte have a fixed number of electrons.
If the light of a specific wavelength is passed through a flame containing that atom, electrons present in different energy levels, known as orbitals, absorb a certain wavelength and excite to higher energy levels.
The extent of absorption ά the number of ground-state atoms in the flame.
Only for information- The ground state is more stable than the excited state. The electrons spontaneously return back to the ground state. It emits the same amount of radiant energy. This process is called fluorescence. Fluorescence is used in atomic emission spectroscopy.
Brief note on - Instrumentation
The basic components of atomic absorption are:
Light source
Chopper
Atomizer
Burners
flames
Monochromators
Detectors
Amplifier
Readout devices
WORKING PROCESS
Calibration
Quantitative analysis in AAS
Safety measures
Important questions and answer
A presentation containing the Principle, shematic diagram, omponents of the instrument, working of the instrument, application, advantages and disadvantages of the instrument.
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.
https://youtu.be/_yLt_abcK2w
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He discussed the concept of quality improvement, emphasizing its applicability to various aspects of life, including personal, project, and program improvements. He defined quality as doing the right thing at the right time in the right way to achieve the best possible results and discussed the concept of the "gap" between what we know and what we do, and how this gap represents the areas we need to improve. He explained the scientific approach to quality improvement, which involves systematic performance analysis, testing and learning, and implementing change ideas. He also highlighted the importance of client focus and a team approach to quality improvement.
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Atomic Absorption Spectroscopy (www.Redicals.com)
1. HISTORY
• The technique was introduced in 1955 by Alan Walsh in
Australia ( 1916 – 1998 ).
• The first commercial atomic absorption spectrometer
was introduced in 1959.
The application of atomic
absorption spectra to chemical
analysis
2. PRINCIPLE
Atomic absorption spectroscopy is a method of elemental
analysis. It is particularly useful for determining trace
metals in liquids and is most independent of molecular
form of the metal in sample.
It is the absorption phenomenon.
When a sample solution is aspirated into the flame, the
solvent is vaporised leaving particles of the solid salt.
The salt burns and converted into the gasses form which
is dissociated into free neutral atoms and some of them
excited by the flame heat. Remaining atoms in the ground
state absorbs light of specific wavelength emitted by the
lamp of same element to be determined and the intensity
of the light absorption is measured.
3. Atomic absorption spectroscopy is a quantitative method of
analysis that is applicable to many metals and a few
nonmetals.
It is very reliable and simple to use.
It can analyze over 62 elements.
Elements detectable by atomic absorption are highlighted in pink in this periodic table
4. BOLTZMANN DISTRUBUTION EQUATION
N*/No = e - ∆E/kT
N* – number of excited atoms
N
o – number of unexcited atoms
∆E – difference in energies of two levels
K – Boltzmann constant
T – temperature of the flame
9. The cathode consists of a hollow cup. In the
cup is the element which is determined.
The anode is tungsten wire. The two
electrodes keep in a tube containing an inert
gas (Ne or Ar).
The lamp window is constructed of quartz,
silica, or glass.
10. When a potential (300-500 V) is applied between two
electrodes, The electric discharge ionizes the inert gas (Ne or Ar
usually) atoms filled in the hollow tube, which in turn, are
accelerated into the cathode with high velocity and sputter
metal atoms into the gas phase. Metal atoms become excited
and after returning to ground state give rise to metal emission
spectrum.
11. The neon or helium gas in the hollow cathode lamp
performs three functions
It dislodges atoms from the surface of the cathode
responsible for excitation of the ground state metal atoms
It is main source of current carrying capacity in the HCL.
• The pressure maintained in the lamp is 1 to 5 torr.
• The spectral lines produced by the HCL are so narrow that
they are completely absorbed by the atoms.
• Each hollow cathode lamp emits the spectrum of the metal
which is used in the cathode, for example copper cathode
emits copper spectrum which is absorbed by copper atoms.
12. 2. Electrodeless Discharge Lamp (EDL)
It is difficult to make stable hollow cathode lamp
from certain elements particularly those that are
volatile, such as arsenic, germanium.
An alternative light has been developed in the EDL. It
consists of an evacuated tube in which the metal of
interest is placed. The tube is filled with argon at low
pressure and sealed off. The sealed tube is then placed
in microwave discharge cavity.
Under these conditions the argon becomes a plasma
and cause excitation of the metal sealed inside the
tube. The emission from the metal is that of its
spectrum.
13. CHOPPER
A rotating wheel is interposed between the hollow
cathode lamp and flame .This rotating wheel is known
as chopper.
It is interposed to break the steady light coming from
the lamp into pulsating light which is used to measure
the intensity of light absorbed by elements without
interference by radiation from the flame itself.
Pulsating light gives pulsating current in photocell.
There is also steady current caused by light which is
emitted by flame. But only pulsating current is
amplified and recorded.
14.
15. ATOMISER
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
Atomiser converts the liquid into small droplets which
are easily vaporised.
Types of atomisers :-
1. Flame atomiser:-
a.) Total consumption burner
b.) premixed burner
2. Non-flame atomiser
16. a). Total consumption burner
In this whole sample is atomised into the flame, hence named as
total consumption burner.
Disadvantages
Noisy and hard to use.
In this burner, the sample solution,
the fuel, and oxidizing gases are
passed through separate passages to
meet at the opening of the base of
flame. Then the flame breaks the
sample in liquid form into the
droplets which are evaporated and
burns. Leaving the residue which is
reduced to atoms.
Fuel used – H2 /acetylene
Oxidant – O 2
17. b). Premixed burner
It is most widely used because of uniformity in flame intensity.
In this the sample solution ,fuel and oxidant are mixed before
they reach the tip.
The fine droplets get carried out along with the fuel gas at outlet,
the large drops of sample get collected in chamber and are drained
out.
Advantages
Non-turbulent
Noiseless
Stable
Disadvantages
Only 5% sample
reaches
to the flame and rest
95% is wasted.
18. Temperature of some flames
Fuel oxidant Temperature (K)
H2 Air 2000-2100
C2H2 Air 2100-2400
H2 O2 2600-2700
C2H2 N2O 2600-2800
For some elements that form refractory oxides (molecules hard
to break down in the flame) nitrous oxide (N2O) needs to be
used instead of air (78% N2 + 21% O2) for the oxidant. In that
case, a slightly different burner head with a shorter burner
slot length is used.
19. Non flame atomiser
The graphite furnace is an electro thermal atomiser
system that can produce temperatures as high as 3,000°C.
The heated graphite furnace provides the thermal energy
to break chemical bonds within the sample held in a
graphite tube, and produce free ground state atoms.
The ground-state atoms are capable of absorbing energy,
in the form of light, and are elevated to an excited state.
The amount of light energy absorbed increases as the
concentration of the selected element increases.
21. GRAPHITE TUBE ATOMIZER:
• 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.
22. NEBULIZATION
Before the liquid sample enters the burner ,it
is converted into droplets this method a
formation of small droplets its called
nebulization
Common method of nebulization is by use of
gas moving at high velocity, called pneumatic
nebulization.
23. MONOCHROMATORS
This is a very important part in an AA spectrometer.
It is used to separate out all of the thousands of lines.
Without a good monochromator, detection limits are
severely compromised.
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.
They are of two types:
1) Prism
2) Grating
24. Prism monochromator :-
Quartz material is used
for making prism, as
quartz is transparent over
entire region
Grating monochromator :-
it consists of a series of
parallel straight lines cut
into a plane surface
26. READ OUT DEVICE
• In the most of AAS measurement, chart
recorders are used as read out device. A
chart recorder is a potentiometer.
27. INTERFERENCE
Interference is a phenomenon in which two waves
superimpose to form a resultant wave of greater or lower
amplitude. Interference decrease the intensity of absorption of
light . Interference usually refers to the interaction of waves
that are correlated or coherent with each other, either because
they come from the same source or because they have the same
or nearly the same frequency.
Types of interferences
1) Spectral interference
2) Chemical interference
3) Physical interference
28. Spectral interferences
Spectral interferences arise when the absorption or emission
of an interfering species either overlaps or lies so close to the
analyte absorption or emission that resolution by the
monochromator becomes impossible. ex:-Manganese triplet
(4031,4033,4035Å) overlapped by gallium line(4033Å).
This interference can be corrected by amplitude modulation
of the source.
Chemical interference
Occurs due to incomplete dissociation of compounds in the
flame when the concentration of compound is more.
Removed by use of higher flame temperature.
Chemically –by addition of more thermally stable compound.
ex-addition of lanthanum to the aluminium and magnesium
for detection of magnesium
29. Physical interference :-viscosity
-solvent
-ionization
1) Viscosity – viscosity is invertionaly proportional to the
intensity of absorption.
2) Solvent – organic solvent increases the intensity and
aqueous solvent decreases the intensity of absorption.
3) Ionization – occurs due to high flame temperature. A
number of vaporized atoms become ionized by the flame.
Resulting ions absorb at a different wavelength than the
vaporized atoms the new wavelength will not be selected by
the monochromator and low results occurs.
Na Na+ + e-
Overcome by addition of more easily ionizable element
Ex- ionization interference of Na is corrected by the addition
of Potassium to the Sodium .
30. APPLICATION
Clinical analysis: Analysing metals in biological fluids such as blood
and urine.
Environmental analysis: Monitoring our environment – eg finding
out the levels of various elements in rivers, seawater, drinking water,
air, petrol and drinks such as wine, beer and fruit drinks.
Pharmaceuticals: In some pharmaceutical manufacturing processes,
minute quantities of a catalyst used in the process (usually a metal)
are sometimes present in the final product. By using AAS the amount
of catalyst present can be determined.
Industry: Many raw materials are examined and AAS is widely used
to check that the major elements are present and that toxic
impurities are lower than specified – eg in concrete, where calcium
is a major constituent, the lead level should be low because it is
toxic.
Mining: By using AAS the amount of metals such as gold in rocks
can be determined to see whether it is worth mining the rocks to
extract the gold.
31. 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