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Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International University Updated on 8/28/2006 Chapter 1

Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International University Updated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry. References: Bernhard Welz: Atomic Absorption, second, completely revised edition, 1985.

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Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International University Updated on 8/28/2006 Chapter 1

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  1. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry • References: • Bernhard Welz: Atomic Absorption, second, completely revised edition, 1985. • J.W. Robinson: Atomic Spectroscopy, Second Edition, Revised and Expended, 1996 • C. Vandecasteele, and C.B. Block: Modern methods for Trace Element Determination, 1997. • Ed. Metcalfe: Atomic Absorption and Emission Spectroscopy, Analytical Chemistry by Open leaning, 1987. • V. Sychra, V. Svoboda, I. Rubeska, Atomic Fluorescence Spectroscopy, Van Nostrand Reinhold Company, London, pp. 379 (1975). • And many others 1.

  2. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry • History of Atomic Spectroscopy • Several thousand years ago: fireworks is an early implementation of atomic emission) • In 1817: Fraunhoffer noted that when radiation from the electrical discharge between two metal electrodes was passed through a prism it produced a spectrum with lines in it. • Year 1902: Wood observed for the first time the atomic fluorescence from excited sodium.

  3. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry • Before 1953: primarily for qualitative analysis • Interpretation of the spectra in solar and interstellar atmospheres, elucidation of which elements were present in those atmospheres • In 1955 and since then: Alan Walsh’s significant contributions (also important works by Alkemade and Milatz in 1955). • Birth of atomic absorption spectrometry (1955) • Recommended as a generally applicable method of analysis • In the following years, it was principally Walsh and his co-workers at Commonwealth Scientific and Industrial Research Organization (CSIRO), Australia who developed atomic absorption into a quantitatively analytical technique of high sensitivity and selectivity. • Some of Walsh’s important contributions:

  4. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry • Some of Walsh’s important contributions • Light source: hollow cathode, thus greatly reducing the resolution required for successful analyses. • Detector: photomultipliers (PMTs), thus eliminating problems associated with the poor measurement sensitivity with a photographic plate. • Modulation: reduces interferences 1.

  5. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry • Year 1964: Winefordner and Vickers (UF) • Proposed AFS (flame) as a new analytical method (Anal. Chem. 1964, 36, 161), http://pubs3.acs.org/acs/journals/toc.page?incoden=ancham&indecade=4&involume=36&inissue=1 • Since then, AFS has gone through a periods of very rapid growth, similar to that of AAS between 1957 and 1965. Much of the credit for this attributed to two research groups in particular: Professor Winefordner and Professor West, Imperial College, London.

  6. http://web.chem.ufl.edu/people/faculty/contact.php?id=9 • “During the 1960s, we were world leaders in developing atomic fluorescence spectroscopy and phosphorimetry for trace analysis. During the 1960s and 1970s, we were world leaders in using signal-to-noise calculations and measurements to optimize atomic and molecular spectrometric methods. In the 1970s to the present, we have been world leaders in the use of lasers in atomic fluorescence spectrometry, atomic emission breakdown spectroscopy, Raman spectrometry and molecular luminescence spectrometry.”

  7. In 1960s : fast development of inductively coupled plasma (ICP) as atomization source in AAS, AFS and AES. There were a number of groups involved in the development of this technique, such as the following: Greenfield, Fassel, and much more!

  8. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry • In the middle to the late 1970s: another milestone in developing use of ICP, in 1974, Gray published a paper in which he used plasma as an ion source for mass analysis. Other important researchers: R.S. Houk (Ames Laboratory, Iowa State University), K.E. Jarves (UK), etc. • Year 1983: birth of the first commercial ICP/MS instrument (initially marketed by VG Isotopes Ltd (UK), and the Canadian Sciex System). • Year 1997: FIU purchased AFS • Year 1998: FIU purchased ICP/MS • Year 2003: FIU purchased DRC ICP/MS • Year 2004: FIU purchased High Resolution ICP/MS

  9. E1 E1 E1 E2 E2 E2 Absorption Emission Fluorescence Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry 2. Principles of AFS 2.1 Atomic fluorescence spectra Three different modes of radiation absorption and release can be distinguished Figure 1. Modes of radiation absorption and release

  10. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry • Atomic absorption Atoms at lower energy levels absorb radiation from a radiation source and the electrons jump to the high energy levels. AA measures the absorbance by the sample. • Atomic emission If the atoms are excited thermally or electrically, then the absorbed energy is released as an emission spectrum. • Atomic fluorescence If the excitation is brought by optical radiation, the atoms only absorb exactly defined amount of energy (i.e. radiation of definite frequency) and an absorption spectrum can be observed. The energy absorbed in this manner is released in the form of a fluorescence spectrum.

  11. Light source Atomizer Monochromator Detector Readout Atomizer Monochromator Detector Readout Atomizer Monochromator Detector Readout Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry AAS AES AFS Light source Figure 2. Schematic block diagram of AAS, AES, and AFS.

  12. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry 2.2 Measuring Fluorescence • AAS Beer’s law has been used in quantitative analysis: T = I1/Io, [1] A = -logT = log Io/I1 = abc [2] Where: T = transmittance I0 and I1 = intensities of incident light and the transmitted light, respectively. A = absorbance C = concentration of target element a: Proportionality constant called Absorptivity

  13. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry • AFS The following mathematical relationships can be derived based the Beer’s law and special aspects of AFS: IF = C’I0N [3] IF = intensity of the measured fluorescence C’ = constant for any particular experimental arrangement I0 = intensity of incident radiation N = number of the atoms that can absorb radiation

  14. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry 2.3. Atomic fluorescence transitions 2.3.1 Resonance fluorescence The fluorescence radiation is of the same wavelength as the absorbed radiation. This type of fluorescence is used most often for quantitative analysis. λF = λA 1 Resonance Fluorescence 0

  15. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry • Three difficulties are involved with resonance fluorescence. • Scattered radiation from the light source by particles in the flame is at the resonance wavelength. This results in a direct analytical interference giving falsely high results. • Self-absorption. The measured fluorescence intensity is decreased. • Interference from stepwise fluorescence

  16. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry 2.3.2 Direct line Direct line Fluorescence occurs when an electron in an excited state emits radiation in returning to a higher electron level than the one from which the electron absorbed radiation. The wavelength of the emitted radiation is longer than the wavelength of the absorbed radiation. λF > λA 2 Direct line fluorescence 1 0

  17. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry • Advantages and Disadvantages of Direct line fluorescence • Eliminates, to some extent, interferences encountered with resonance such as scattered radiation and increased excited atom population • A quite inefficient process • Oscillation strength of the absorption transition between the ground state and the second excited state is lower than that between ground and first excited state. • Only a small fraction of these excited atoms will descend to the first excited state prior to fluorescence rather than to the ground state.

  18. Interferences from the metal in the light source Transition between the 2nd and 1st states is one that is also common to the metal in the source, and it is very likely that this line will be an emitted line from the source itself. This radiation can reach the atomizer and can be scattered in the same way as the resonance line, resulting in a falsely high fluorescence signal Solution: insertion of a filter between the light source and the atomizer, which does not permit the radiation of this wavelength from source to reach the atomizing system.

  19. 2 1 0 Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry 2.3.3 Stepwise line In stepwise line fluorescence, different upper levels are involved in the excitation-deexcitation processes λF > λA Stepwise line fluorescence

  20. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry • Advantages and Disadvantages of Direct line fluorescence • Distinctly lower intensity than resonance fluorescence, even though it occurs at the as wavelength as resonance fluorescence. • Oscillator strength of the transition between the ground and the higher excited state is lower than in resonance line. • Of the excited atoms, only a fraction will descend to the lower excited state by a nonradiation process.

  21. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry 2.3.5 Sensitized fluorescence Atom of one species (donor) is excited radiationally and then transfers its excitation energy to an atom of the same or another species (acceptor) by collision. The acceptor then undergoes radiative deactivation, resulting in atomic fluorescence. The process can be represented as follows: A + hvA A* A* + B  A + B* B*  B + hvF where A is the donor and B is the acceptor.

  22. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry 2.4. Several concepts • Stokes fluorescence The fluorescence radiation has a longer wavelength than the absorbed radiation, i.e. if λF > λA. If λF < λA, the transition is termed anti-stokes. • Quenching The intensity of the atomic fluorescence is diminished by the collision between excited atoms and other molecules in the atomization sources. • Self-absorption The emitted photons from excited electron levels re-absorbed by ground state atoms in light path, resulting in decreased fluorescence intensity. • Quantum efficiency Quantum efficiency is the ratio of the energy emitted in fluorescence to the energy absorbed, per unit of time)

  23. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry 2.5 Parameters affecting the intensity of the fluorescence • Concentration of atoms in the atomizer This is the base used for quantitative analysis. • Extent of self-absorption Fraction of emitted radiation self-absorbed by similar ground state atoms • Intensity of the radiation from the source of excitation (as in all fluorescence techniques) If the source power is constant, the intensity of fluorescence radiation will be linear with ground state atom concentration. A increase in sensitivity can be obtained by increasing the source power. This is a different point with AAS, in which atomization system is the most important part.

  24. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/26/2008 Chapter 1 Atomic Fluorescence Spectrometry 2.6 Quenching Since the quenching process is very important in atomic fluorescence, a few examples are given below. • The excess electronic energy of the excited atoms is converted into translational energy of the colliding species without involving the internal energy of the latter. For instance, this quenching can be processed by collision with free atoms: A* + B  A + B or with free electrons: A* + e-  A + e-

  25. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2008 Chapter 1 Atomic Fluorescence Spectrometry 2. The excess electronic energy of the excited atoms is released on collision, resulting in the changes of electronic or vibrational/rotational energy of the colliding species. For instance, quenching by collision with other atoms: A* + B  A + B* or with molecules: A* + BC  A + BC* Depending on the experimental conditions used, some of these quenching processes can significantly affect the fluorescence radiance. The quenching process is especially important for AFS and has been taken into consideration in the design of the atomizer. The order of quenching efficiency for some gases is Ar<H2<H2O<N2<CO<O2<CO2 .

  26. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry 3. Advantages and limitations 3.1 Advantages • IF can be increased by increasing I0, the incident radiation. The use of lasers greatly extends this range. • C’ can be increased by increasing L, the size of the flame and the quantum efficiency. • N, the number of fluorescence atoms, is a function of the unexcited neutral atoms in the system. This is inherently higher than the number of thermally excited atoms. • The IF is linearly related to the concentration of the sample element over a wide concentration range. • The element may be excited at one wavelength and the fluorescence measured at a different wavelength. This eliminates the effects of scattered radiation. • High sensitivity are claimed for some elements (lead, mercury, arsenic, selenium, ……..)

  27. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2008 Chapter 1 Atomic Fluorescence Spectrometry 3.2 Limitations • Self – absorption. This leads to a reversal of the slope of the curve relating If the concentration of the element at high concentrations. • Only one element or maximum several elements can be analyzed simultaneously. • IF may suffer from background interferences by the atomizer (flame). • Laser radiation sources can increase the IF, subsequently the sensitivity. However, the operation of the system is expensive and difficult. And there is no commercially available instrument.

  28. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry • Instrumentation • Radiation source • Atomizer • Wavelength selection system • Signal detector • Electronic readout system

  29. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry 4.1. Excitation Sources • spectral line sources • continuum sources. Since the intensity of the fluorescence radiance is proportional to the intensity of the exciting radiation, sources with high radiance are required in order to achieve a good sensitivity and linear range. A major part of the effort devoted to improvement of AFS instrumentation in recent years has been concerned with the excitation source.

  30. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry 4.1.1 Hollow Cathode Lamp Conventional HCL

  31. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry • a tungsten anode and a cylindrical cathode • neon or argon at a pressure of 1 to 5 torr • The cathode is constructed of the metal whose spectrum is desired or served to support a layer of that metal 4.1.1 Hollow Cathode Lamp (Cont’d) • Ionize the inert gas at a potential of ~ 300 V • Generate a current of ~ 5 to 15 mA as ions and electrons migrate to the electrodes. • The gaseous cations acquire enough kinetic energy to dislodge some of the metal atoms from the cathode surface and produce an atomic cloud. • A portion of sputtered metal atoms is in excited states and thus emits their characteristic radiation as they return to the ground sate • Eventually, the metal atoms diffuse back to the cathode surface or to the glass walls of the tube and are re-deposited

  32. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry 4.1.1 Hollow Cathode Lamp (Cont’d) • High potential, and thus high currents lead to greater intensities • This advantage is offset somewhat by an increase in Doppler broadeningof the emission lines from the lamp • Self-absorption: the greater currents produce an increased number of unexcited atoms in the cloud. The unexcited atoms, in turn, are capable of absorbing the radiation emitted by the excited ones. This self-absorption leads to lowered intensities, particular at the center of the emission band Doppler broadening?

  33. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry http://en.wikipedia.org/wiki/Doppler_effect Doppler effect? A source of waves moving to the left. The frequency is higher on the left, and lower on the right. A stationary microphone records moving police sirens at different pitches depending on their relative direction

  34. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry Improvement……. • Most direct method of obtaining improved lamps for the emission of more intense atomic resonance lines is to separate the two functions involving the production and excitation of atomic vapor • Boosted discharge hollow-cathode lamp (BDHCL) is introduced as an AFS excitation source by Sullivan and Walsh. • It has received a great deal of attention and a number of modifications to this type of source have been conducted.

  35. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry Boosted discharge hollow-cathode lamp (BDHCL)

  36. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry Operation principle of BDHCL • A secondary discharge (boost) is struck between an efficient electron emitter and the anode, passing through the primary atom cloud. • The second discharge does not produce too much extra atom vapor by sputtering the walls of the hollow cathode, but does increase significantly the efficiency in the excitation of sputtered atom vapor. • This greatly reduces the self-absorption resulting from simply increasing the operating potential (increase Doppler broadening and self-absorption) to the primary anode and cylindrical cathode.

  37. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry 4.1.2 Electrodeless Discharge Lamps (EDL)

  38. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry Electrodeless discharge lamps (EDL) • A typical lamp is constructed from a sealed quartz tube containing a few torr of an inert gas such as argon and a small quantity of the metal of interest (or its salt). • The lamp does not contain an electrode but instead is energized by an intense field of radio-frequency or microwave radiation. • Radiant intensities usually one or two orders of magnitude greater than the normal HCLs. • The main drawbacks: their performance does not appear to be as reliable as that of the HCL lamps (signal instability with time) and they are only commercially available for some elements.

  39. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2008 Chapter 1 Atomic Fluorescence Spectrometry 4.1.3 Xenon Arc Lamps • High-pressure xenon-arc lamps, producing a stable and intense continuum source • The lamp produces intense radiation by the passage of current through an atmosphere of xenon. • The spectrum is continuous over the range between 250 and 600 nm, with the peak intensity about 500 nm. • Readily employed for multielemental analysis • Its intensity falls off severely below about 210 nm, thus making it unsatisfactory for the analysis of some environmentally important elements such as arsenic and selenium.

  40. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry 4.1.4 Laser Sources • high intensity • narrow bandwidths • coherent nature of their outputs Laser-induced fluorescence (LIF) offers a very sensitive and selective spectroscopic method, which has a low susceptibility to spectral interferences. Allows nonresonance transition lines to be used for many elements.

  41. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry 4.2. Atomizers Basic requirements: • Efficient and rapid production of free atoms with minimum background noise • Long residence time of the analyte atoms in the optical path • Low quenching properties The order of quenching efficiency for some gases is Ar<H2<H2O<N2<CO<O2<CO2. • Low cost of operation and ease of handling.

  42. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry 4.2.1 Miniature diffusion flames (cool flames) • Diffusion flame is generally applied to the flames in which the oxidant necessary for combustion is fully supplied by diffusion and/or entrainment from the surrounding atmosphere. • Argon is generally used as carry gas and hydrogen is used as fuel. The temperature of theseargon-hydrogen-air flames ranges from 280-850 C, depending on the flame region selected. • Atomizer is generally made of quartz • Why diffusion flame? • How diffusion flame works?

  43. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2008 Chapter 1 Atomic Fluorescence Spectrometry Atomization mechanism in diffusion flame: • The atomization at such low temperature (about 800 C) is not because of thermal decomposition, but is due to free radicals in the flame. • Quartz has a strong catalytic effect at temperature around 800 C and H radical can be formed by decomposition of hydrogen molecules at the quartz surface. • Unsaturated oxygen atoms at the surface bind hydrogen molecules and an H atom torn away (Welz and Melcher, Analyst, 1983, 108, 213-224). H + O2 = OH + O [1] O + H2 = OH + H [2] OH + H2 = H2O + H [3]

  44. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry • Because 1) the equilibrium constant of reaction [3] is very large (K3 = 0.21e7645/T), 2) the hydrogen concentration in the atomizer is much higher than the water concentration, H radicals outnumber OH radicals at least a few orders of magnitude. • The atomization of volatile hydride-forming elements in heated quartz cell are due to the collision with free H radical according to: MHx + H = MHx-1 + H2 MH + H = M + H2 For example: SeH2 + H = SeH + H2 SeH + H = Se + H2

  45. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry 4.2.2 Electrothermal Atomizers 4.2.3 Cold-Vapor Technique for Mercury Mercury is the only metallic element that exhibits an appreciable atomic vapor pressure at ambient temperature. 4.2.4. Miscellaneous Atomization Techniques • Inductively coupled plasma (ICP) • Microsecond pulsed glow discharge

  46. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry • Comparison of AFS with AA and Flame AES • Sensitivity and detection limit: generally AFS> or = AAS > AES • Linear range: AFS > AAS >AES • Analytical cost: AFS (except LIF) < AAS and AES • Operator skill required: similar (except LIF) • Commercial availability: AAS and AES > AFS

  47. Advanced Analytical Chemistry – CHM 6157 ® Y. CAI Florida International UniversityUpdated on 8/28/2006 Chapter 1 Atomic Fluorescence Spectrometry

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