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INTRODUCTION OF ATOMIC ABSORPTION SPECTROSCOPY
PRESENTOR:
BUSHRA IQBAL(11740)
HISTORYThe beautiful phenomenon of “RAINBOW”
was the first dispersed spectrum.
In 1665 NEWTON took the first and the most important step towards the development of spectroscopy.
In 1859 G.R KIRCHOFF and R BUNSEN emerged as the FATHER OF MODERN SPECTROSCOPY.
SPECTROSCOPY The study of structure of atom or molecules.
Used in analysis of wide range of sampleCan classify in atomic or molecular spectroscopy.
ATOMIC SPETROCOPY
MOLECULAR SPECTROSCOPY
ABSORPTION SPECTROSCOPY
• It gives the measurement of absorbed energy by the atom or molecule after which it excite and gives the absorbed energy in the form of absorption spectrum
ATOMIC ABSORPTION SPECTROSCOPY
• Atomic absorption spectroscopy is a technique for determining the concentration of a particular metal element in a sample. Atomic absorption spectroscopy can be used to analyze the concentration of over 62 different metals in a solution.
TYPES OF ATOMIC SPECTRA
1) ATOMIC EMISSION SPECTRA:
2) ATOMIC ABSORPTION SPECTRA:
3) ATOMIC FLUORESCENCE SPECTRA
COMPARISON
ATOMIC EMISSION SPECTROSCOPY• Examines the wavelengths of
photons emitted by atoms or molecules during their transition from an excited state to a lower energy state.
• Each element emits a characteristic set of discrete wavelengths.
• By observing these wavelengths the elemental composition of the sample can be determined.
ATOMIC ABSORPTION SPECTROSCPY• Measures the loss of
electromagnetic energy after it illuminates the sample under study.
• The energy in certain amount is absorbed during transition to the higher level.
• The amount of energy absorbed gives estimate of the concentration of the analyte in the sample.
PRESENTORS:
RIMSHA ISMAIL (11780)RUTABA MURTAZA (11782)
PRINCIPLE OF ATOMIC ABSORPTION SPECTROSCOPY
• Absorption therefore is carried out by unexcited atoms.
THEORY OF ATOMIC ABSORPTION SPECTROSCOPY
CONCEPT OF ATOMIC ABSORPTION SPECTROSCOPY
• In 1955, A. WALSH and another one of C T J ALKAMADE and J M W MILATZ.
PRINCIPLE OF ATOMIC ABSORPTION SPECTROSCOPY
SOURCE SOURCE SOLUTION SOLUTION EVAPORATION
MIST MIST VAPORIZATION
SOLID SOLID GAS GAS DISSOCIATION
THERMAL EXCITATION THERMAL EXCITATION
FLAME EMISSION FLAME EMISSION
hv
RE-EMISSION (FLUORESCENCE)RE-EMISSION (FLUORESCENCE)
ABSORPTION OF RADIANTENERGY
ABSORPTION OF RADIANTENERGY
hv2
MONOCHROMATERMONOCHROMATER
DETCETOR DETCETOR AMPLIFIER AMPLIFIER
RECORDER RECORDER
• The total amount of light absorbed may be given mathematically by the following expressions:
Total number of light absorbed = πe2/mc Nf Where, e= is the charge on the electron of mass m= mass of electron c= is the speed of light N= is the total number of atoms that can absorb at frequency in the light path v= frequency f= is the oscillator strength or ability of each atom to absorb at frequency π= is constant The above equation can be written as:
Total amount of light absorbed= Constant x N x f
INSTRUMENTATION OF ATOMIC ABSORPTION SPECTROSCOPY
1. RADIATION SOURCE
The main sources used for atomic absorption are:I. Hollow Cathode Lamp (HCL)II. Electrode less Discharge Lamp (EDL)
I. HOLLOW CATHODE LAMP
II. ELECTRODELESS DISCHARGE LAMP
SOURCE MODULATION
2. ATOMIZERS
There are two types of atomizers which are used in Atomic Absorption Spectroscopy.
• Flame Atomizers• Electrothermal Atomizers
FLAME ATOMIZERS ELECTROTHERMAL ATOMIZERS
PRESENTOR:
SIDRA JILANI(11795)QURRATULAIN SHAMS RIZVI(11776)
BASIC PRINCIPLE OF FLAME ATOMIZERS:
FLAME ATOMIZER:• Flame is used to atomize the sample• Sample when heated is broken into its atoms
PRINCIPLE:• High temperature of flame causes excitation• Electrons of the atomized sample are promoted to higher
orbitals, by absorbing certain amount of energy
QUANTITATIVE ANALYSIS:• The amount of energy absorbed is specific for a particular
element (for electronic transition).• Amount of absorbed radiation is a quantitative measure for the
concentration of the element to be analyzed
SEQUENCE OF STEPS IN A FLAME ATOMIZER
SAMPLE NEBULIZER ASSEMBLY
CONVERSION INTO FINE MIST
& SMALL DROPLETS OF
SOLUTION
ASPIRATED INTO SPRAY CHAMBER (MIXING
CHAMBER)
AEROSOL MIXES WITH
COMBUSTION GASES
FLAME(ATOMIZATION
OCCURS)
Sample to be
nebulized is taken
(aspirated) via a
capillary tube
Nebulizer:sample+fue
l+oxidant
fine mist or aerosol
Atomization occurs
A thin Flame is produced
Mixture is carried to the flame
NEBULIZER
CONSTRUCTION:
FLAME ATOMIZER
FUEL OXIDANT TEMPERATURE, OC
MAXIMUM BURNING VELOCITY
(CM S-1)
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
FUELS & OXIDANTS USED FOR FLAME COMBUSTION
FLAME STRUCTUREFLAME ABSORBANCE PROFILE
MONOCHROMATOR
1)
2)
3) - Wavelength selectors- Produces
monochromatic light
Consists of:1) Entrance slit
2) Diffraction grating3) Exit slit
Diffraction gratings are mostly used rather than
prisms
Electro thermal atomizer first appeared on the market in the early 1970s
HISTORY
ELECTRO THERMAL ATOMIZATIONElectro thermal atomization (ETA) (also known as Graphite furnace atomization)
Used for improvement and betterment in the limit-of-detection and sensitivity for atomic absorption measurements.
GRAPHITE FURNACE ATOMIZERS:Atomizer is a ‘Graphite
tube’ therefore it is known as
the Graphite furnace atomic
absorption spectroscopy (GFAAS).
More convenient
to use a non-flame
method that is the electrically
heated graphite
tube .
GRAPHITE FURNACE ATOMIZER CONSTRUCTION:
Graphite tube •serves as sample cell. ( heating part of the graphite furnace).
Enclosed water cooled housing
•Metal jacket by which the water is circulated .
Transparent windows
•Made of quartz allow light to pass through the tube.
Inert purge gas control •protect graphite tube from oxidation
Electrical contact •Heating of graphite tube
Atomization of sample
1.Drying
2. Ashing or pyrolysis
3.Atomization
PROCESS IN ATOMIZERS:
DETECTOR
CONSTRUCTION:
PHOTO MULTIPLIE
R TUBE
Photocathode
Dynodes (electrod
es)
Glass Envelop
Anode
WORKING OF PHOTOMULTIPLIER TUBE
• Photo Emission • Secondary Emission
Operation of photomultip
lier tube
Video0003.3gp
The signal could be displayed for readout in the readout devices.
READOUT DEVICE :
Readout devices:• Digital
voltmeter • Simple
galvanometer• Potentiomete
r• Computer
TOPICS: 1. SINGLE AND DOUBLE BEAM AA SPECTROPHOTOMETERS2. SAMPLE PREPARATION
SOBIA JAVEDROLL NO:11796
Types Of AA Spectrophotometers• Atomic Absorption spectrophotometric measurements are
done extensively by using; Single-Beam AA Spectrophotometer Double-Beam AA Spectrophotometer
HISTORY• The first AAS was presented by Walsh and co-workers in
Melbourne in 1954, was a double beam atomic absorption spectrophotometer.
• Walsh worked with Perkin-Elmer, the first AAS instrument developed by that company was MODEL 303.
Single Beam AA Spectrophotometer:
• Working Principle: Single beam measurements are depended upon the varying
intensity of a single beam of light having a single optical path. That is why called as single beam AA spectrophotometer.
Working Diagram:
Double Beam AA Spectrophotometer:Working principle: • It split the light from the source into a ‘sample beam’
(focused to the sample cell) and a ‘reference beam’ (focused around the sample cell).
• Such an instrument is called as double beam AA spectrophotometer, as measurements are made on varying intensity of double beams of light in dual optical path.
Working Diagram
COMPARATIVE ANALYSIS OF BOTH INSTRUMENTS: Single Beam Instruments Double Beam Instruments Simple, Less expensive, less complexity Complex, more expensive, not easily made
Low automation, more efficiency of light High speed automation, less light efficiency
More time consuming Less time consuming
Low stability Increased stability
Depend upon single beam intensity Depend upon ratio between both beams
More chances of fluctuations Lesser fluctuations in readings
Sample and Reference placed separately Sample and Reference are kept at same time
High light throughput, more resolution Less light throughput, decreased resolution
More warm-up time is required Less or reduced warm-up time required
SAMPLE PREPARATION• The preparation of the sample solution for a solid material is most time consuming step of process of analysis in an atomic absorption spectroscopy. It involves following steps;
Weighing of sample
Dissolution in appropriate solvent or digestion using different techniques
Dilution of sample if necessary
CATEGORIES• A sample employed for atomic absorption spectroscopy in the
laboratory is placed into one of the following categories:• Considerations are to be given to some of the general principles involved in the various sample preparations.
Aqueous Solutions
Organic Solutions
Inorganic Solutions
Organic Solids
Gases
Aqueous Solutions:• A little preparation is required with this sort of sample.• These include samples in raw and treated water, sea waters,
biological fluids, beer, plating solutions, effluents, wines etc.
Organic Liquids:• It include petroleum products, many of which can be directly
be aspired. Examples of such solvents used are m-heptene, aliphatic ketones, (e.g. methyl iso butyl ketone) aliphatic esters, alcohols and xylene, cyclohexanes, isopropanol etc. are frequently employed.
• Note: When samples are analyzed in organic solvents some adjustments such as ‘BURNER CONTROLS’, proper ventilation or other appropriate settings must be used.
Inorganic Solids:• These include solid samples of fertilizers, ceramics, alloys or
rocks. • These are solvated by using appropriate aqueous or acid
medium depending on solubility. Such as hot water, concentrated acids, acidic mixtures, dilute acids etc.
• Other techniques can also be employed such as fusion prolonged acid digestion, wet ashing etc to yield sample solutions.
Organic Solids:• These includes typically material of foods, leaves, tissue, biological
solids, polymers, plants, feedstuff etc. • Before solublization of such samples, there is a requirement of
destruction via wet digestion or ashing in a furnace (muffle).
Gases: • Atomic absorption analytical works or procedures can be employed in analyzing gases indirectly as liquid sample.PREPARATION:
Separate metals from gas
Using Millipore filter disc
Techniques Used For Certain Sample Preparations:
• As discussed in previous topics, some solid sample requires special techniques for dissolution. Such sample preparation requires time and proper handling.
Wet Ashing Or Wet Digestion:
Inorganic samples
Undissolved in aqueous solvents
Treated with acids
Such as Perchloric acid, HCl, HNO3,
Digestion of complexes,
silicates
Dry Ashing:
Weighed sample Heated in furnace (muffle) Mix left over in acid
Remove inorganic particles like lead
or mercury Microwave Dissolution: (type of digestion)
Sealing of sample in microwave
vessel
Addition of suitable acids
Keeping temperature at 100-200oC with
increased pressure
Less dissolution time, clear liquid
sample of biological materials
Extraction and Concentration process:• Such an operation is done if sample contain species
interfering in absorption or the concentration of sample desired is in low concentration to show absorption readings. Such a process involves,
Solvent Extraction
Liquid- Liquid Extraction
Ion Exchange methods
DILUTION• The viscosity adjustment can be done with suitable solvents which can be that in a way solvent should; o Dissolve or mix completely with the sampleo Well burnt but in a controlled manner o Be in pure state such that possessing no species having
molecular absorption in regiono Not yield harmful by-productso Not be expensive
PRESENTOR:
Shumaila Eliyas
INTERFERENCES IN ATOMIC ABSORPTION SPECTROSCOPY
“Increase or decrease in the size of the signal obtained from the analyte as a result of the presence of some other known or unknown component in the sample”
Types of interference: Spectral interferenceChemical interference
INTERFERENCE
Spectral interference This may be caused by direct overlap of the
analytical line with the absorption line of the matrix element.
HOW TO OVERCOME ?By choosing an alternate analytical
wavelengthBy removing the interfering element from the
sample.
Examples of spectral interferences
Chemical interference
Formation of compound of low volatility
Decrease in calcium absorbance is observed
with increasing concentration of sulfate
or phosphate
By increasing flame temperatureUse of releasing agents (La 3+ ) Cations react with the interferent releasing
the analyte Use of protective agents: They form stable but volatile compounds with
analyte.
How to overcome?
Ionization interference
Ionization of ground state gaseous atom with in a flame will reduce extent of absorption in AAS.
M ↔ M+ + e
HOW TO MINIMIZE: Low temperature of the flame Addition of an excess of ionization suppressant e.g. the alkali
metals (K, Na, Rb, and Cs)
Influence of potassium on the ionization of barium
ATOMIC ABSORPTION SPECTROSCOPY
OF
PRESENTOR:
SHAZIA A.GHAFFAR
Pharmaceutical
Biological
Biochemical
For detection of purity and consistency of these trace metals
Also for quantitative determination of metals mainly in solid sample as mineral, ores and alloys
For Quantitative & Qualitative Analysis:
• Magnesium in cast iron
• Silver, Zinc, Copper and Lead in Cadmium metal
DETERMINATION OF
TRACE COPPER IN NICKEL METAL
• Method of multiple standard addition
• A plot of absorbance against the amount of standard can be used to determine the amount of copper in a sample.
ASSAYS OF TRACE METALS
Determination of trace metal in a silicon foam cavity wound dressing
Zinc in Zinc insulin suspension and tetracosactrin Zinc injection
Copper and Iron in ascorbic acid
Aluminum in albumin solution and Ca, Mg, Mercury
Zinc in water used for diluting haemodialysis solution
BIOLOGICAL & BIOCHEMICAL ANALYSIS
•For the analysis of pharmaceutically or therapeutically essential component of formulation, such as Zinc in Zinc-insulin, minerals in multivitamin-mineral preparation and Ca, Mg, Al in antacids.
•To establish concentration limits where the metal is regarded as an impurity.
PHARMACEUTICAL ANALYSIS
•Mining industries
•Petroleum industries
•Determination of metallic elements in food industry like Copper, Zinc and Nickel in vegetable oil and copper in beer.
INDUSTRIAL ANALYSIS