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Chapter 9

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.

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Chapter 9

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  1. Chapter 9 Atomic Absorption and Atomic Fluorescence Spectrometry

  2. 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.

  3. Flame Atomization

  4. Flame Structure

  5. Flame Atomizer

  6. Flame Atomizer

  7. 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

  8. Specialized Atomization Techniques • Glow Discharge Atomization • Hydride Atomization • Cold-Vapor Atomization

  9. Flame Atomic Absorption Spectroscopy

  10. Radiation Sources • Doppler Broadening • Pressure Broadening • Electrodeless Discharge Lamps • Source Modulation • Hollow Cathode Lamps:

  11. 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

  12. Spectrophotometers • Single-Beam • Double-Beam

  13. 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

  14. Chemical Interference The equilibria of principle interest include: • Formation of Compounds of Low Volatility • Dissociation Reactions • Ionization

  15. Calibration Curves • Should follow Beer’s Law

  16. Standard Addition Method

  17. 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

  18. 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

  19. 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/

  20. 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

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