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ATOMIC ABSORPTION SPECTROSCOPY

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ATOMIC ABSORPTION SPECTROSCOPY

  1. 1. ATOMICATOMIC ABSORPTIONABSORPTION SPECTROSCOPYSPECTROSCOPY Presented by : MOHAMMED WAQAR SIDDIQUIPresented by : MOHAMMED WAQAR SIDDIQUI
  2. 2. CONTENTS:CONTENTS:  Principle of AAS.Principle of AAS.  Instrumentation.Instrumentation.  Applications.Applications.  Test perform in AKU.Test perform in AKU.
  3. 3. INTRODUCTION:INTRODUCTION:  Atomic Absorption Spectroscopy is a very commonAtomic Absorption Spectroscopy is a very common technique for detecting metals and metalloids intechnique for detecting metals and metalloids in samples.samples.  It is very reliable and simple to use.It is very reliable and simple to use.  It can analyze over 62 elements.It can analyze over 62 elements.  It also measures the concentration of metals in theIt also measures the concentration of metals in the sample.sample.
  4. 4. HISTORY:HISTORY: The first atomic absorption spectrometer was built byThe first atomic absorption spectrometer was built by CSIRO scientist Alan Walsh in 1954. Shown in theCSIRO scientist Alan Walsh in 1954. Shown in the picture Alan Walsh(left), with a spectrometer.picture Alan Walsh(left), with a spectrometer.
  5. 5. Elements detectable by atomic absorption are highlighted in pink in thisElements detectable by atomic absorption are highlighted in pink in this periodic tableperiodic table
  6. 6. PRINCIPLE:PRINCIPLE:  The technique uses basically the principle that freeThe technique uses basically the principle that free atoms (gas) generated in an atomizer can absorbatoms (gas) generated in an atomizer can absorb radiation at specific frequency.radiation at specific frequency.  Atomic-absorption spectroscopy quantifies theAtomic-absorption spectroscopy quantifies the absorption of ground state atoms in the gaseous state .absorption of ground state atoms in the gaseous state .  The atoms absorb ultraviolet or visible light and makeThe atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels. The analytetransitions to higher electronic energy levels. The analyte concentration is determined from the amount ofconcentration is determined from the amount of absorption.absorption.
  7. 7. - Concentration measurements are usually determined from aConcentration measurements are usually determined from a working curve after calibrating the instrument with standardsworking curve after calibrating the instrument with standards of known concentration.of known concentration. - Atomic absorption is a very common technique forAtomic absorption is a very common technique for detecting metals and metalloids in environmental samplesdetecting metals and metalloids in environmental samples..
  8. 8. THEORY:THEORY: Detector Monochromator Atomizer Nebulizer Hollow Cathode Lamp Atomic Absorption spectrometer
  9. 9. Schematic diagram of AAS:Schematic diagram of AAS:
  10. 10. LIGHT SOURCE:LIGHT SOURCE:  Hollow Cathode Lamp are the most common radiationHollow Cathode Lamp are the most common radiation source in AAS.source in AAS.  It contains a tungsten anode and a hollow cylindricalIt contains a tungsten anode and a hollow cylindrical cathode made of the element to be determined.cathode made of the element to be determined.  These are sealed in a glass tube filled with an inert gasThese are sealed in a glass tube filled with an inert gas (neon or argon ) .(neon or argon ) .  Each element has its own unique lamp which must beEach element has its own unique lamp which must be used for that analysis .used for that analysis .           
  11. 11. NEBULIZER:NEBULIZER:  suck up liquid samples at controlled rate.suck up liquid samples at controlled rate.  create a fine aerosol spray for introduction into flame.create a fine aerosol spray for introduction into flame.  Mix the aerosol and fuel and oxidant thoroughlyMix the aerosol and fuel and oxidant thoroughly for introduction into flame.for introduction into flame.
  12. 12. AtomizerAtomizer  ElementsElements to be analyzed needs to be in atomic sate.to be analyzed needs to be in atomic sate.  AtomizationAtomization isis separation of particles into individualseparation of particles into individual molecules and breaking molecules into atoms. This ismolecules and breaking molecules into atoms. This is done by exposing the analyte to high temperatures in adone by exposing the analyte to high temperatures in a flame or graphite furnace .flame or graphite furnace .
  13. 13. ATOMIZERS:ATOMIZERS: ATOMIZER FLAME ATOMIZERS GRAPHITE TUBE ATOMIZERS
  14. 14. FLAME ATOMIZERFLAME ATOMIZER::  To create flame, we need to mix an oxidant gas and aTo create flame, we need to mix an oxidant gas and a fuel gas.fuel gas.  in most of the cases air-acetylene flame or nitrous oxide-in most of the cases air-acetylene flame or nitrous oxide- acetylene flame is used.acetylene flame is used.  liquid or dissolved samples are typically used with flameliquid or dissolved samples are typically used with flame atomizer.atomizer.         
  15. 15. GRAPHITE TUBE ATOMIZERGRAPHITE TUBE ATOMIZER::  uses a graphite coated furnace to vaporize the sample.uses a graphite coated furnace to vaporize the sample.  ln GFAAS sample, samples are deposited in a smallln GFAAS sample, samples are deposited in a small graphite  coated tube which can then be heated tographite  coated tube which can then be heated to vaporize and atomize the analyte.vaporize and atomize the analyte.  The graphite tubes are heated using a high currentThe graphite tubes are heated using a high current power supply.power supply.
  16. 16. MONOCHROMATOR:MONOCHROMATOR:  This is a very important part in an AA spectrometer. It isThis is a very important part in an AA spectrometer. It is used to separate out all of the thousands of lines.used to separate out all of the thousands of lines.  A monochromator is used to select the specificA monochromator is used to select the specific wavelength of light which is absorbed by the sample,wavelength of light which is absorbed by the sample, and to exclude other wavelengths.and to exclude other wavelengths.  The selection of the specific light allows theThe selection of the specific light allows the determination of the selected element in the presence ofdetermination of the selected element in the presence of others.others.
  17. 17. DETECTOR:DETECTOR:  The light selected by the monochromator is directed ontoThe light selected by the monochromator is directed onto a detector that is typically a photomultiplier tube , whosea detector that is typically a photomultiplier tube , whose function is to convert the light signal into an electricalfunction is to convert the light signal into an electrical signal proportional to the light intensity.signal proportional to the light intensity.  The processing of electrical signal is fulfilled by a signalThe processing of electrical signal is fulfilled by a signal amplifier . The signal could be displayed for readout , oramplifier . The signal could be displayed for readout , or further fed into a data station for printout by thefurther fed into a data station for printout by the requested formatrequested format..
  18. 18. Calibration CurveCalibration Curve  A calibration curve is used to determine the unknownA calibration curve is used to determine the unknown concentration of an element in a solution. The instrumentconcentration of an element in a solution. The instrument is calibrated using several solutions of knownis calibrated using several solutions of known concentrations. The absorbance of each known solutionconcentrations. The absorbance of each known solution is measured and then a calibration curve ofis measured and then a calibration curve of concentration vs absorbance is plotted.concentration vs absorbance is plotted.  The sample solution is fed into the instrument, and theThe sample solution is fed into the instrument, and the absorbance of the element in this solution isabsorbance of the element in this solution is measured .The unknown concentration of the element ismeasured .The unknown concentration of the element is then calculated from the calibration curvethen calculated from the calibration curve
  19. 19. APPLICATIONS:APPLICATIONS: Determination of even small amounts of metals (lead,Determination of even small amounts of metals (lead, mercury, calcium, magnesium, etc) as follows:mercury, calcium, magnesium, etc) as follows:  Environmental studies: drinking water, ocean water, soil.Environmental studies: drinking water, ocean water, soil.  Food industry.Food industry.  Pharmaceutical industry.Pharmaceutical industry.
  20. 20. TEST IN AKUTEST IN AKU LEAD COCENTRATION.LEAD COCENTRATION. ZINC COCENTRATION.ZINC COCENTRATION. COPPER COCENTRATION.COPPER COCENTRATION.
  21. 21. REFERENCES:REFERENCES:  Vogel’s Textbook of Quantitative AnalysisVogel’s Textbook of Quantitative Analysis, G. Svehla,, G. Svehla, Pearson.Pearson.  Principles of Instrumental AnalysisPrinciples of Instrumental Analysis, Skoog., Skoog.  Basic Concepts Of Analytical chemistryBasic Concepts Of Analytical chemistry, S M Khopkar., S M Khopkar.

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