Chapter 9 Atomic Absorption (AAS).pdf - Principles of...

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2014/9/101Principles of Instrumental AnalysisChapter 9Atomic Absorption (AAS) and Atomic Fluorescence Spectrometry (AFS)P.231Ch9Atomic Absorption and Atomic Fluorescence SpectrometryFIGURE 9-1 Processes occurring during atomization. 9A Sample Atomization Techniques (flame and electrothermal atomization)9A-1 Flame AtomizationAtomization(原子化) is the critical step in flame spectrometry and limits its precision.
2014/9/102TABLE 9-1Properties of flamesP.231Ch9Atomic Absorption and Atomic Fluorescence SpectrometryTypes of Flames:FIGURE 9-2Regions in a flame. P.231Ch9Atomic Absorption and Atomic Fluorescence SpectrometryFlashback (火舌回閃): burning velocity > gas flow rateGas flow rate >> burning velocity will blow off the burner.Free atoms
2014/9/103FIGURE 9-3Temperature profiles in degrees Celsius for a natural gas-air flame. P.232Ch9Atomic Absorption and Atomic Fluorescence SpectrometryFlame structurePrimary combustion zone(Blue)Interzonal regionSecondary combustion zoneFIGURE 9-4Flame absorption profiles for three elements. P.232Ch9Atomic Absorption and Atomic Fluorescence SpectrometryMg: No. of Mg atom increases and then decreases at secondary combustion zone due to formation of oxides.Ag: not easily oxidized. The absorption increases with exposure time.Cr: forms very stable oxides.
2014/9/104FIGURE 9-5 A laminar-flow burner. P.233Ch9Atomic Absorption and Atomic Fluorescence SpectrometryFlame Atomizer:The most reproducible of all liquid-sample-introduction method.

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