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Chapter 9
Atomic Absorption and Atomic Fluorescence Spectrometry
Atomic SpectroscopyAtomization is by
far the most critical step in atomic spectroscopy.
In AAS and AFS there are two factors involved.
The intensity of light source.
The probability of transition.
Flame Atomization
Flame Structure
Flame Atomizer
Flame Atomizer
Electrothermal AtomizersGraphite furnace atomic absorption spectrometry (GFAAS) is also
known by various other acronyms, including electrothermal atomic absorption spectrometry (ETAAS).
An ideal graphite furnace should fulfill the following requirements: A constant temperature in time and space during the interval in
which free atoms are produced Quantitative atom formation regardless of the sample
composition Separate control of the volatilization and atomization processes High sensitivity and good detection limits
A minimum of spectral interferences
Specialized Atomization Techniques
Glow Discharge Atomization Hydride Atomization Cold-Vapor Atomization
Flame Atomic Absorption Spectroscopy
Radiation Sources Doppler Broadening Pressure BroadeningElectrodeless Discharge Lamps Source Modulation Hollow Cathode Lamps:
Spectrophotometers In general, the instrument must contain: Narrow bandwidth to isolate the line chosen for measurement Sufficient glass filter Interchangeable interference filters Good-quality ultraviolet/visible monochromators Photomultiplier tubes
SpectrophotometersSingle-BeamDouble-Beam
Spectral Interferences The Two-Line Correction Method The Continuum-Source Correction
Method Background Correction Based on the
Zeeman EffectBackground Correction Based on the
Source Self-Reversal
Chemical Interference
The equilibria of principle interest include:Formation of Compounds of Low
VolatilityDissociation Reactions Ionization
Calibration CurvesShould follow Beer’s Law
Standard Addition Method
InstrumentationSources: Hollow Cathode Lamp- only
observed the fluorescent signal during pulses
Electrodeless Discharge Lamp- produced intensities that exceed those of hollow cathode lamps
Lasers- ideal source with high intensities and narrow bandwidths
InstrumentationDispersive Instruments- They are made up of a
modulated source, an atomizer, a monochromator or an interference filter system, a detector, and a signal processor and readout.
Nondispersive Instruments- They ideally are made up of a source, an atomizer, and a detector.
Advantages: Simplicity and low-cost instrumentation Ready adaptability to multi-element analysis High-energy throughput and thus high sensitivity Simultaneous collection of energy from multiple lines,
enhancing sensitivity
References www.anachemumu.se.htm www.aurora-instr.com/right.htm www.anachem.umu.se/jumpstation.htm www.anachem.umu.se/cgi/jumpstation.exe?AtomicSpectroscopy www.anachem.umu.se/cgi/jumpstation.exe?OpticalMolecularSpectroscopy www.minyos.its.rmit.edu.au/~rcmfa/mstheory.html http://science.widener.edu/sub/ftir/intro_it.html http://www.s-a-s.org/ http://www.chemsw.com http://www.scimedia.com/chem-ed/spec/atomic/aa.htm http://nercdg.org http://www.analyticon.com www.lcgmag.com/ www.lcms.com/
References www.dq.fct.unl.pt/QOF/Chroma.html www-ssg.chem.utas.edu.au/ www.yahoo.com/science/chemistry/chromatography/ www.onlinegc.com http://www.scimedia.com/chem-ed/analytic/ac-meth.htm http://www.scimedia.com/chem-ed/spec/atomic/aa.htm http://www.scimedia.com/chem-ed/spec/atomic/afs.htm http://www.cee.vt.edu/program_areas/environmental/teach/smprimer/aa/
aa.html#Features http://www.anachem.umu.se/aas/gfaas.htm http://www.agsci.ubc.ca/fnh/courses/food302/atomic/
aatomic03.htm#electro http://www.scpscience.com/products/AA/hollowlamps.asp http://las.perkinelmer.com/catalog/Product.aspx?ProductId=N3050691 http://elchem.kaist.ac.kr/vt/chem-ed/spec/atomic/aa.htm