Lecture 6 - Optical atomic spectrometry and UVvisible...

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Optical atomic spectrometry and UV- visible molecular absorption spectrometry
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Spectrophotometers in AA Source modulation helps remove emission from flame (line source or spectrum) Instrument must have narrow enough bandwidth to see specific lines. Filters or monochromators (1Å) Single beam instruments Double beam instruments Why use a double beam instrument?
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Interferences in AA Spectral interferences From source—rare with narrow hollow-cathode sources From flame—absorption or scatter by combustion products Matrix—absorption or scatter by components of sample Not common with flame atomization and can be avoided If interfering species is known then excess can be added to dilute out amount in sample matrix Standard addition Chemical interferences More common than spectral interferences Compounds that have low volatility are formed with anions and reduce fraction of atomized sample Can use protective agents such as EDTA Dissociation equilibria Ionization equilibria Factor in higher temperature flames
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Releasing agents, protective agents, etc What is a releasing agent? What is a protective agent? What is an ionization suppressor?
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Sample prep and calibration limitations of AA Flame spectroscopic techniques require a liquid (aqueous) phase sample Limits applicability in soil, tissue, mineral, etc. analysis Electrothermal atomization allows direct atomization
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Lecture 6 - Optical atomic spectrometry and UVvisible...

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