Atomic Absorption and Atomic Fluorescence Spectroscopy by Pnh6FNS9

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									Chapter 9

   Atomic Absorption and Atomic
   Fluorescence Spectrometry
Atomic Spectroscopy
Atomization 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 Atomizers
Graphite 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 Broadening
 Electrodeless 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
Spectrophotometers
 Single-Beam
 Double-Beam
Spectral Interferences
 The Two-Line Correction Method
 The Continuum-Source Correction
  Method
 Background Correction Based on the
  Zeeman Effect
 Background Correction Based on the
  Source Self-Reversal
Chemical Interference
The equilibria of principle interest include:
 Formation of Compounds of Low
  Volatility
 Dissociation Reactions
 Ionization
Calibration Curves
 Should   follow Beer’s Law
Standard Addition Method
Instrumentation
Sources:
 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
Instrumentation
Dispersive 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?OpticalMolecularSpectrosc
    opy
   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/a
    a/aa.html#Features
   http://www.anachem.umu.se/aas/gfaas.htm
   http://www.agsci.ubc.ca/fnh/courses/food302/atomic/aatomic03.htm#el
    ectro
   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

								
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