An Introduction to Optical Atomic Spectrometry

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An Introduction to Optical Atomic Spectrometry
Chapter 8
Chapter 8
Chapter 8
Chapter 8
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2
Energy Level Diagram Sodium
5
7s
6p
6p
6s
5d
5p
5p
5682
5s
4
4d
4p
4p
5688
3d
6160
4s
8183
3
6154
Energy, electron volts
8195
11404
3p
3p
2
3302
11382
3303
2852.8
1
5690
2853
5696
0
3s
3
Energy level diagram for Mg
10
4p
4p
3d
3d
4s
8
2798
2791
6
2936
Energy, electron volts
2929
3p
3p
4
2803
2796
2
0
3s
4
Energy Level Diagram for Atomic Magnesium
Singlet
Triplet
8
7s
5d
6s
7s
6p
6p
6p
5p
6s
4f
5s
4d
5p
5p
5p
4d
4d
5s
4p
6
3d
4p
4p
4p
12083
3d
Energy, electron volts
4s
5528
4s
14871
5711
3p
8807
5167
3838
4
11820
3832
5173
2852
3p
3p
3p
3829
2026
5184
2
4751
0
3s
5
Flame Emission Spectrum of Sodium
5682.7 5688.2 A
5890 and 5896 A
Relative intensity
Wavelength A
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Fluorescence of Thallium Atom
6s27s2 S1/2
l 535.0 nm
6s26p2 P3/2
l 377.6nm
6s26p2 P1/2
Energy level diagram of thallium
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Line Width

• Line broadening is due to
• Uncertainty effect
• Doppler effect
• Pressure effect
• Electric and magnetic field effect

l0
P
Absorbance or emitted power
P1/2
Dl1/2
8
The uncertainty effect

• The uncertainty principle
• Dn . Dt gt1
• Dt 210-8
• Dl10-5 nm

9
The Doppler Effect
10
Pressure Broadening
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Types of Atomizers Used for Atomic Spectroscopy Types of Atomizers Used for Atomic Spectroscopy
Typical atomization Temperature oC Type of Atomizer
1700-3150 Flame
1200-3000 Electrothermal vaporization ETV
4000-6000 Inductively coupled plasma ICP
4000-6000 Direct current plasma DCP
2000-3000 Microwave induced argon plasma MIP
Nonthermal Glow discharge plasma
4000-5000 Electric arc
40000 ? Electric spark
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Methods of Sample Introduction in Atomic Spectroscopy Methods of Sample Introduction in Atomic Spectroscopy
Type of sample Method
Solution or slurry Pneumatic nebulization
Solution Ultrasonic nebulization
Solid, liquid, solution Electrothermal vaporization
Solution of certain elements Hydride generation
Solid, powder Direct insertion
Solid, metal Laser ablation
Conducting solid Spark or arc ablation
Conducting solid Glow discharge sputtering
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Sample Introduction Methods

• Solution
• Solid

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Pneumatic Nebulizer

• Solution samples are introduced to the atomizer
  by means of a nebulizer.
• Nubulizers convert the liquid to a fine mist
  called aerosol.
• The most common nebulizer is the concentric-tube

15
Concentric Tube Pneumatic Nebulizer
High-velocity gas breaks the liquid up into fine
droplets.
High velocity gas flow
Capillary tube
Suction
Sample
Gas inlet
High pressure gas flow
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Cross-Flow Pneumatic Nebulizer
High pressure gas flow
Sample
17
Fritted Disk Pneumatic Nebulizer
Sample
High pressure gas flow
18
Babington Pneumatic Nebulizer
Solution film
Sample
High pressure gas flow
19
Ultrasonic Nebulizer

• The sample is pumped to a piezoelectric crystal
  that vibrates at 20 kHz to several MHz.
• Produces more dense and uniform aerosols than
  pneumatic nebulizers.

20
Electrothermal Nebulizer

• A small amount of a liquid is placed on a
  conductor such as carbon rod and an electric
  current heats up the rod and evaporates the
  sample into an argon gas stream.

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Hydride Generation

• For elements such as
• Sb
• Pb
• Sn
• Se
• As
• 3 BH4- 3H 4 H3AsO3 3 H3BO3 4 AsH3 3 H2O

Sample and NaBH4
Inert gas
Stirrer
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Introduction of Solid Samples

• Direct sample insertion
• Electrothermal vaporization
• Arc and spark ablation
• Laser ablation

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Suggestions Appreciated! Shiraz University,
Department of Chemistry, IRAN nzmaleki_at_gmail.com