
Content 3.1. Theoretical Concepts 3.2. Atomic Absorption Instrumentation 3.3. Graphite Furnace Atomic Absorption 3.4. Control of Analytical Interferences | | 2
3.1. Theoretical Concepts • The Atomic Absorption Process • Theoretical Concepts • Quantitative Analysis • Characteristic Concentration • Detection Limits | | 3
Fig3-2 Grotrian diagrams for K Fig 3-3Grotrian diagrams for Na | | 5
2. Theoretical Concepts⑴Integral Formula of AASFig 3-4 Typical Shape of A Atomic Absorption line | | 7
Integral Absorption FormulaBy atomic theory (3.1) By Line Shape Function ( the Nature distribute ) (3.2) The Peak Absorption Coefficient k0 is: (3.3) | | 8
⑵ Peak Absorption Theoryby Lambert-Beer’s Law: (3.4) (3.5) (3.6) | | 9
The Absorbance is: (3.7) | | 10
When: va>> ve, and v0a= v0e, then kv≈k0, | | 11
(3.8) | | 12
(3.9) (3.10) | | 13
3. Quantitative Analysis (3.10) | | 14
4. Characteristic Concentration (3.11) | | 15
5. Detection Limit (3.12) | | 16
1. Photometers for AAS | | 19
1. Photometers for AAS | | 20
2. line source (Hollow Cathode Lamp ) Fig 3-13 | | 22
Hollow Cathode Lamp Emission Process Fig 3-14 | | 23
Fig 4-19 Tree Type Burner Head for different Type Flame | | 26
4. Control of Analytical Interferences Ionization interference Matrix interference Chemical interference Background interference | | 28
Ionization Interference Ba → Ba+ + e- K → K+ + e- | | 29
Matrix Interference | | 30
Chemical Interference | | 31
Background Interference | | 34
(4.13) AHCL= Aa+ Ab (4.14) AD2=Ab, (4.15) Aa = AHCL- AD2 | | 36
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 | | 37
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 | | 38
THGA graphite tube Fig 4-27 | | 39
The Graphite Furnace Power Supply and Programmer • A Graphite Furnace Temperature Program • Drying • Pyrolysis • Cool Down(optional) • Atomization • Clean Out • Cool Down | | 40