chapter 9 atomic absorption and atomic fluorescence spectrometry 1
TRANSCRIPT
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Chapter 9Atomic Absorption and Atomic
Fluorescence Spectrometry
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1. Atomic Absorption Spectrometry
2. Atomic Fluorescence Spectrometry
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9A SAMPLE ATOMIZATION TECHNIQUES
9A-1 Flame Atomization
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Figure 9-1 Processes occurring during atomization.
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Types of Flames
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TABLE 9-1 Properties of Flames
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Flame Structure
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Figure 9-2 Regions in a flame.
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Figure 9-3 Temperature profiles in C for a natural gas-air flame.
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Figure 9-4 Flame absorbance profile for three elements.
Figure 9-5 A laminar flow burner. 11
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Performance Characteristics of Flame Atomizers.
1. Reproducible (CV = 1% or better)
2. low sensitivity
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9A-2 Electrothermal Atomization
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Figure 9-6 (a) Cross-sectional view of a graphite furnace. (b) The L’vov platform and its position in the graphite furnace.
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Performance Characteristics of Electrothermal Atomizers.
1. high sensitivity ( DL = 10-10 to 10-12 g)
2. low relative precision ( CV = 5-10%)
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9A-3 Specialized Atomization Techniques Glow Discharge Atomization Hydride Atomization Cold-Vapor Atomization
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Figure 9-8 (a) Cross section of a cell for glow-discharge atomization of solid samples. (b) Craters formed on sample surface by six jets of ionized argon.
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Figure 9-9 A hydride generation and atomization system for Atomic Absorption Spectrometry.
ATOMIC ABSORPTION INSTRUMENTATION
radiation sourcesample holder
wavelength selectordetector
signal processor & readout
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Figure 9-10 Absorption of a resonance line by atoms.
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Figure 9-11 Schematic cross section of a hollow-cathode lamp.
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Figure 9-12 Cutaway of an electrodeless discharge lamp.
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9B-2 Spectrophotometers
Single-Beam InstrumentsDouble-Beam Instruments
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Figure 9-13 Typical flame spectrophotometers: (a) single-beam design and (b) double beam design.
9C INTERFERENCES IN ATOMIC ABSORPTION
SPECTROSCOPY
Spectral InterferencesChemical Interferences
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Formation of Compounds of Low Volatilityreleasing agents
protective agents ( EDTA, 8-hydroxy quinoline, ammonium
pyrrolidinedithiocarbamate)
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Dissociation EquilibriaMO M + O M(OH)2 M + 2OHNaCl Na + Cl
Ionization EquilibriaM M+ + e
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TABLE 9-2 Degree of Ionization of Metals at Flame Temperatures
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9E ATOMIC FLUORESCENCE SPECTROSCOPY
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