C hapter 3 atomic absorption spectroscopy
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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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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


3.1. Theoretical Concepts

  • The Atomic Absorption Process

  • Theoretical Concepts

  • Quantitative Analysis

  • Characteristic Concentration

  • Detection Limits


The Atomic Absorption Process


Fig3-2 Grotrian diagrams for K

Fig 3-3Grotrian diagrams for Na


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


Integral Absorption FormulaBy atomic theory

(3.1)

By Line Shape Function

( the Nature distribute )

(3.2)

The Peak Absorption Coefficient k0 is:

(3.3)


⑵ Peak Absorption Theoryby Lambert-Beer’s Law:

(3.4)

(3.5)

(3.6)


The Absorbance is:

(3.7)


When:

va>> ve,

and

v0a= v0e,

then kv≈k0,


(3.8)


(3.9)

(3.10)


3. Quantitative Analysis

(3.10)


4. Characteristic Concentration

(3.11)


5. Detection Limit

(3.12)


3.2. Atomic Absorption Instrumentation


1. Photometers for AAS


1. Photometers for AAS


A New Type Photometer for AAS


2. line source (Hollow Cathode Lamp )

Fig 3-13


Hollow Cathode Lamp Emission Process

Fig 3-14


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


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


4. Control of Analytical Interferences

Ionization interference

Matrix interference

Chemical interference

Background interference


Ionization Interference

Ba → Ba+ + e-

K → K+ + e-


Matrix Interference


Chemical Interference


The Method Of Standard Additions


Background Interference


(4.13)

AHCL= Aa+ Ab

(4.14)

AD2=Ab,

(4.15)

Aa = AHCL- AD2


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


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


THGA graphite tube

Fig 4-27


  • 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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