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