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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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