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C hapter 3 Atomic Absorption Spectroscopy

C hapter 3 Atomic Absorption Spectroscopy. 3.1. Theoretical Concepts 3.2. Atomic Absorption Instrumentation 3.3. Graphite Furnace Atomic Absorption 3.4. Control of Analytical Interferences. 3.1. Theoretical Concepts. The Atomic Absorption Process Theoretical Concepts

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C hapter 3 Atomic Absorption Spectroscopy

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  1. Chapter 3 Atomic Absorption Spectroscopy 3.1. Theoretical Concepts 3.2. Atomic Absorption Instrumentation 3.3. Graphite Furnace Atomic Absorption 3.4. Control of Analytical Interferences

  2. 3.1. Theoretical Concepts • The Atomic Absorption Process • Theoretical Concepts • Quantitative Analysis • Characteristic Concentration • Detection Limits

  3. The Atomic Absorption Process

  4. Fig3-2 Grotrian diagrams for K Fig 3-3Grotrian diagrams for Na

  5. 2. Theoretical Concepts⑴Integral Formula of AASFig 3-4 Typical Shape of A Atomic Absorption line

  6. Integral Absorption FormulaBy atomic theory (3.1) By Line Shape Function ( the Nature distribute ) (3.2) The Peak Absorption Coefficient k0 is: (3.3)

  7. ⑵ Peak Absorption Theoryby Lambert-Beer’s Law: (3.4) (3.5) (3.6)

  8. The Absorbance is: (3.7)

  9. When: va>> ve, and v0a= v0e, then kv≈k0,

  10. (3.8)

  11. (3.9) (3.10)

  12. 3. Quantitative Analysis (3.10)

  13. 4. Characteristic Concentration (3.11)

  14. 5. Detection Limit (3.12)

  15. 3.2. Atomic Absorption Instrumentation

  16. 1. Photometers for AAS

  17. 1. Photometers for AAS

  18. A New Type Photometer for AAS

  19. 2. line source (Hollow Cathode Lamp ) Fig 3-13

  20. Hollow Cathode Lamp Emission Process Fig 3-14

  21. 3. Atomizer for AAS (Pre-Mix Burner System)

  22. Fig 4-19 Tree Type Burner Head for different Type Flame

  23. 4. Control of Analytical Interferences Ionization interference Matrix interference Chemical interference Background interference

  24. Ionization Interference Ba → Ba+ + e- K → K+ + e-

  25. Matrix Interference

  26. Chemical Interference

  27. The Method Of Standard Additions

  28. Background Interference

  29. (4.13) AHCL= Aa+ Ab (4.14) AD2=Ab, (4.15) Aa = AHCL- AD2

  30. 3.3. Graphite Furnace Atomic Absorption • Graphite furnace atomizer components • The Graphite Furnace Power Supply and Programmer • Quantitative analysis GFAAS • Effect of Matrix on Height and Area

  31. 1. Graphite furnace atomizer components The Graphite Furnace Atomizer A basic graphite furnace atomizer is comprised of the following components: · graphite tube · electrical contacts · enclosed water cooled housing · inert purge gas controls

  32. THGA graphite tube Fig 4-27

  33. The Graphite Furnace Power Supply and Programmer • A Graphite Furnace Temperature Program • Drying • Pyrolysis • Cool Down(optional) • Atomization • Clean Out • Cool Down

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