1. Atomic Absorption and Atomic Fluorescence Spectrometry
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Atomic Absorption and
Atomic Fluorescence
Spectrometry
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2. Atomization Processes
Solution of
analyte
Atomization Processes
Spray
Nebulization
Desolvation
Solid/gas
aerosol
Gaseous
molecules
Volatilization
Excited
molecules
hn molecular
Dissociation
(reversible)
Atoms
Excited
atoms
hn atomic
Atomic ions
Ionization
(reversible)
Excited ions
hn ionic

4. Regions in a Flame Stable molecular oxides Secondary combustion zone
Interzonal region
Primary combustion zone
Rich in free atoms
C2, CH and other radicals

5. Temperature Profile in oC for a Natural Gas /Air Flame5
1863
1858
1830
1800 4
1750
1700
1600 3
1400
Distance above orifice cm 2 1
Burner tip

6. Stable products
Atoms

7. Flame Absorbance profile for Some Elements
Absorption Cr Ag Mg
Height cm

8. The Premixed Burner
Fuel Oxidant

9. Laminar-flow burner

16. Graphite Furnace
3000
Atomize
600
Ash
150
Dry oC

17. Graphite Furnace Cooled electrical connections
External gas inlet
Graphite tube
Entrance window
Exit window
L’vov platform
Internal gas inlet

18. 6/3/2018

19. Output Signal 0.8 Ash 0.7 0.6 0.5 0.4 0.2 0.3 2 mL of canned juice 0.1
Dry
Atomize
0.05
0.1
0.0
Standards mg/L Sample

20. Electrothermal atomizer

21. Graphite Furnace

23. Atomic Absorption Instrumentation
Radiation Sources
Hollow cathode lamps
Electrodless discharge lamps
Source modulation
Spectrophotometers
Single beam
Double beam

24. Radiation Sources Atomic lines are narrow (0.002-0.005nm).
In chapter 13: Beer’s law is obeyed when line width of the source is narrower than absorption line width.
When ordinary spectrophotometers with continium source is used nonlinear calibration curves are obtained.
Line sources are used

25. Hollow Cathode Lamp Hollow cathode Anode Quartz or pyrex Ne or Ar at
1-5 torr
Quartz or pyrex
window
Glass shield

26. Sputtering

30. Typical Single Beam Flame Atomic Absorption Spectrophotometer
Detector
Lamp supply
Ebert monochromator
Burner

32. Interferences in Atomic Absorption Spectroscopy
Spectral Interferences
Chemical Interferences

33. Spectral Interferences
Line
Broadband
Scattering nm

34. Scattering
Absorption

35. Background Correction
Signal = ( Background + Signal ) – ( Backgound )

36. Continuum Source Method
Monochromator at analytical wavelength: signal + background are measured
Slit is opened, source is replaced by deuterium lamp (continuum source):
tiny amount of light is absorbed by sample and the rest is scattered by backgound.
Signal = the difference
Monochromator bandwidth

37. Schematic of a continuum source background
Deuterium lamp
Analyte Hollow
cathode lamp
To monochromator
Electrothermal
atomizer
Chopper
Schematic of a continuum source background
correction system

38. Chemical Interferences
Formation of Compounds of Low Volatility
Anion
Cation
To eliminate the effect:
Higher temperature
Releasing agents
Protective agents

39. Chemical Interferences
Dissociation Equilibria
MO M + O
M(OH) M + 2 OH
Ionization Equilibria
M M+ + e-