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Atomic absorption spectroscopy
Atomic absorption spectroscopy is a technique that uses the absorption of light to measure the concentration of atomic absorption in a sample. It works by vaporizing the sample into atoms, then measuring how much light is absorbed by the atoms at a specific wavelength. The amount of absorption is directly related to the concentration of the element being measured. The key components of an atomic absorption spectroscopy system are the lamp sources, which emit specific wavelengths of light corresponding to the element being analyzed, the atomization process which turns solid or liquid samples into gaseous atoms, detectors that convert light signals into electrical signals, and monochromators that isolate the desired wavelength of light. Potential sources of interference must also be considered and addressed. Common applications of atomic absorption spectroscopy
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Atomic absorption spectroscopy
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- 3. SPECTROSCOPY • Spectroscopy isthe branch of science that deals with the study of interaction of electromagnetic radiations with matter i.e. atoms or molecules of drugs. • Spectroscopy is of two types, Emission spectroscopy and absorption spectroscopy.
- 4. TYPES OF SPECTROSCOPY EMISSIONSPECTROSCOPY Examples include: • Fluorimetry • Flame photometry • Atomic emission spectroscopy. ABSORPTION SPECTROSCOPY Examples include: • UV/Visible spectroscopy • IR spectroscopy • Nuclear Magnetic Resonance Spectroscopy (NMR) • Atomic Absorption Spectroscopy
- 5. ATOMIC SPECTROSCOPY • AtomicSpectroscopy is the result of phenomenon of absorption, emission or fluorescence by atoms or elementary ions mostly in ultraviolet region. • The spectra are obtained by converting the component into gaseous atoms or elementary ions by suitable heat treatments.
- 6. TYPES OF ATOMICABSORPTION SPECTROSCOPY AAS Atomic Absorption Spectra Atomic Emission Spectra Atomic Fluorescence Spectra
- 7. ATOMIC LINE WIDTHAND PRINCIPLE OF ATOMIC ABSORPTION SPECTROSCOPY BY: MAZNA SALEEM
- 8. ATOMIC LINE WIDTH •The width of atomic lines are of considerable importance in atomic absorption or atomic emission spectroscopy. • Narrow lines are highly desirable for both absorption and emission spectroscopy because they reduce the possibility of interferences due to overlapping spectra.
- 9. PRINCIPLE OF AAS: The technique uses basically the principle that free atoms (gas) generated in an atomizer can absorb radiation at specific frequency. Atomic-absorption spectroscopy quantifies the absorption of ground state atoms in the gaseous state . The atoms absorb ultraviolet or visible light and make transitions to higher electronic energy levels. The analyte concentration is determined from the amount of absorption.
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- 11. DEFINITION • Spectrophotometer isan instrument that measures the amount of Light absorbed by a sample as function of wavelength.
- 12. PROPERTIES • It isa techniques are used to measure the concentration of solutes in a solution. • It is the quantitative measurement of the reflection or transmission properties of a material. • It is use in various fields such as chemistry, physics, biochemistry, and chemical engineering and clinical applications.
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- 14. HOW DOES ITWORK?
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- 16. RADIATION SOURCES • AbsorptionLines are very much narrow (0.002 to 0.005) • This limited lines creates problem in AAS. • The problem's solution is nothing but the Radiation Sources.
- 17. LAMP SOURCES A separatelamp source is needed for each element or sometimes group of element. • Hollow Cathode lamp • Electrodeless discharge lamp.
- 18. HOLLOW CATHODE TUBE Apparatus: •Tungston anode. • Cylindrical cathode. • Glass container. Ionization of inert gas occurs when it is supplied with: • 300V potential • 5 to 20mV current.
- 19. WORKING OF HCL •HCL works by the process of sputtering. ‘Sputtering occurs when the energy to be transformed into gaseous atom and bring out an atomic cloud by shifting some amount of metal from the cathode.’ • The excited metal atoms of the atomic cloud emits the radiation. • Metal atom diffuse back thus re-deposition occurs.
- 20. ELECTRODE LESS DISCHARGELAMP • Small amount of both inert gas and the element to be studied is placed inside the tube constructed with quartz glass. • Unlike HCL it is devoid of any electrodes but alternatively microwave radiation is present to provide power from outside the lamp.
- 21. WORKING OF EDL •EDL is available foe wide variety of elements. It is more efficacious practically but expensive.
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- 23. MONOCHROMATOR The function ofthe monochromator is to isolate narrow band width of light (monochromatic light) from the light source.
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- 25. TYPES OF MONOCHROMATOR •Prism • Diffraction grating
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- 28. SOURCE MODULATION It isa process to discriminate light coming from radiation source and flame (atomizer).
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- 31. ATOMIZATION • Component ofatomic absorption spectroscopy. • Device of flame photometry. • Solid or liquid sample is converted into gaseous state.
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- 34. MISCELLANEOUS ATOMIZATION • Onlycertain elements are atomized. • Involves chemical reaction. • By producing volatile hydrides.
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- 36. DETECTORS The role ofthe detector is to convert a light signal into an electrical signal.
- 37. TYPES OF DETECTORS •Photo Tube • Photomultiplier Tube
- 38. PHOTO TUBE • Itconsists of Semi- cylindrical cathode (containing loosely bounded electrons) and central metal wire anode. • The current produce from the photo tube are quite small so it require amplification.
- 39. PHOTOMULTIPLIER TUBE • Theprinciple of operation is the emission of electrons upon exposure to radiation. • The detector contains a photo emissive cathode and a series of dynodes.
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- 41. INTERFERENCES (i) Spectral Interferences, (ii)Chemical Interferences, and (iii) Ionization Interferences.
- 42. SPECTRAL INTERFERENCES This typeof interference normally takes place when the absorption of an interfering species either overlaps or lies very near to the analyte absorption. Examples of spectral interferences, • Combustion products. • Emission line of element, radical or molecule and unresolved band spectra. • Sample Matrix
- 43. CHEMICAL INTERFERENCES • Itresults from various chemical processes occurring during atomization that alter the absorption characteristics of the analyte. • More common. • effects may often be minimized by appropriate choice of experimental parameters.
- 44. • Examples : (i)Chemical Interferences due to Anion (PO43–) (ii) Chemical Interference due to Cations.
- 45. PROTECTIVE AGENTS : Theseagents are found to inhibit the interferences by virtue of their ability to form relatively stable but volatile species with the respective analyte. (a) EDTA. (b) 8-Hydroxyquinoline, and (c) Ammonium salt of APDC.
- 46. IONIZATION INTERFERENCES The substitutionof air with either oxygen or nitrous oxide gives rise to temperatures which are high enough to cause appreciable ionization. Hence, as a consequence of the attained equilibrium-a fairly significant concentration of electron exists. M M + e–
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- 48. SINGLE BEAM SPECTROPHOTOMETER • Itutilizes one beam of light that passes through the sample and the intensity of the light reflected from a reference is measured without sample.
- 49. ADVANTAGES • Low cost •High throughput • High sensitivity • Less complicated • Economical DISADVANTAGES • Calibration should be done with blank and sample continuously according to wavelength and absorption power of sample so reference beam is not obtain simultaneously. • Time consuming
- 50. DOUBLE BEAM SPECTROPHOTOMETER It utilizestwo beams of light: reference and sample beam. Double beam spectrophotometer use rotating mirror to separate the reference beam from a sample beam.
- 51. ADVANTAGES Double beam ismore advantageous then single beam. • High speed • High stability • Flexibility DISADVANTAGES • expensive • Lower sensitivity • Lower reliability
- 52. APPLICATIONS OF AAS BY:FARAH DEEBA
- 53. APPLICATIONS • One ofthe most widely used techniques. • Its popular for quantitative analysis a) molecular weight determination b) detection of conjugation c) detection of functional groups • and qualitative analysis. a) detection of impurities to analyze substance purity . • Assay of trace metals and determination elements. • Importance of AAS In its modern form.
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