Fluorescence spectrometry principles

Atomic Fluorescence Spectrometry. Principles of Quantitative Analysis... 

Principles and Characteristics Atomic fluorescence spectrometry (AFS) is based on excitation of atoms by radiation of a suitable wavelength (absorption), and detection and measurement of the resultant de-excitation (fluorescence). The only process of analytical importance is resonance fluorescence, in which the excitation and fluorescence lines have the same wavelength. Nonresonance transitions are not particularly analytically useful, and involve absorption and fluorescence photons of different energies (wavelength). 

In principle, the difference between X-ray fluorescence spectrometry and electron-probe microanalysis lies in the fact that the analytical information is provided, in the first case, by secondary, fluorescence X-rays, and in the second by primary X-rays, emitted as a result of the impact of the electron beam on the sample s electrons. 

The basic theory, principles, sensitivity, and application of fluorescence spectrometry (fluorometry) were discussed in Chapter 8. Like the UV absorption detector described above, the HPLC fluorescence detector is based on the design and application of its parent instrument, in this case the fluorometer. You should review Section 8.5 for more information about the fundamentals of the fluorescence technique. 

A collection of corrected excitation and emission spectra can be found in Miller J. N. (Ed.) (1981) Standards for Fluorescence Spectrometry, Chapman and Hall, London. Corrected emission spectra can also be found in Appendix 1 of Lakowicz J. R. (1999) Principles of Fluorescence Spectroscopy, Kluwer Academic/ Plenum Publishers, New York. 

Non-linear concentration/response relationships are as common in pesticide residue analysis as in analytical chemistry in general. Although linear approximations have traditionally been helpful the complexity of physical phenomena is a prime reason that the limits of usefulness of such an approximation are frequently exceeded. In fact, it should be regarded the rule rather than the exception that calibration problems cannot be handled satisfactorily by linear relationships particularly as the dynamic range of analytical methods is fully exploited. This is true of principles as diverse as atomic absorption spectrometry (U. X-ray fluorescence spectrometry ( ), radio-immunoassays (3), electron capture detection (4) and many more. 

With the development of the photomultiplier tube the measurement of very low light intensities has become relatively simple and the photoelectric recording of fluorescence emission spectra can now compete in terms of sensitivity with the less convenient photographic method. During the last decade the development of the experimental technique has gained considerable impetus as a result of the requirements of analytical chemists for methods of extreme sensitivity. A variety of spectro-fluorimeters have been described in the literature and commercial instruments of high sensitivity are also available. Recent reviews1-2 deal with the principles and analytical applications of fluorescence spectrometry and a textbook of biochemical applications has been published.2... 

X-ray fluorescence spectrometry (XRF) is a non-destructive method of elemental analysis. XRF is based on the principle that each element emits its own characteristic X-ray line spectrum. When an X-ray beam impinges on a target element, orbital electrons are ejected. The resulting vacancies or holes in the inner shells are filled by outer shell electrons. During this process, energy is released in the form of secondary X-rays known as fluorescence. The energy of the emitted X-ray photon is dependent upon the distribution of electrons in the excited atom. Since every element has a unique electron distribution, every element produces... 

J. D. (1979) Atomic fluorescence spectrometry basic principles and applications, Prog Anal Spectrosc 2 1-183. 

Figure 12.8 The two mtegories of detectors used for energy dispersive X-ray fluorescence spectrometry. (a) Proportional counter used in pulse mode (b) Cooled Si/Li diode detector using Peltier effect (XR detector by Amptek Inc.) (c) Functioning principle of a scintillation detector containing a large size reverse polarized semi-conductor crystal. Each incident photon generates a variable number of electron-hole pairs. The very high quantum yield enables the use of low power primary sources of X-rays (a few watts or radio-isotopic sources).

X-ray fluorescence spectrometry, gas chromatography and neutron activation analysis (NAA). An older book edited by Hofstader, Milner and Runnels on Analysis of Petroleum for Trace Metals (1976), includes one chapter each on principles of trace analysis and techniques of trace analysis and others devoted to specific elements in petroleum products. Markert (1996) presents a fresh approach to sampling, sample preparation, instrumental analysis, data handling and interpretation. The Handbook on Metals in Clinical and Analytical Chemistry, edited by Seiler,... 

Atomic absorption spectrophotometry already then in its second edition. Price (1974) (Analytical Atomic Absorption Spectrometry) published about thelOth book on AAS since inception of the technique with the aim of being a textbook on practical AAS (FAAS). It contains the usual introduction to principles, instrumenttation and analytical techniques, with a large detailed chapter of applications to different materials followed by details for individual elements. A nice expanded version of the author s first book (Price 1979) on Spectrochemical Analysis by Atomic Absorption, includes newer developments such as EAAS. Kirkbright and Sargent (1974) (Atomic Absorption and Fluorescence Spectrometry) produced a massive, excellent, comprehensive treatise on the techniques of atomic absorption and fluorescence spectrometries, with details on... 

Although no sharp lines can be drawn between nuclear and non-nuclear techniques (see De Goeij and Bode, 1997 for a review), the principle of the nuclear technique says that the analytical information on element and concentration originates from the nucleus and not from the atom. As such, chemical binding, chemical compound or matrix composition has no essential influence on the accuracy of the results (Bode and Wolterbeek, 1990 De Goeij and Bode, 1997). It should be noted here that although techniques such as particle/proton induced X-ray emission (PIXE) and X-ray fluorescence spectrometry (XRF) are basically derived from the behaviour of inner orbital electrons rather than the nucleus itself, they are often counted as a nuclear technique, primarily because inner orbital electrons do not predominate in the characteristics of the atom s chemical behaviour (but see also De Goeij and Bode, 1997 for NMR and Mdssbauer techniques). 

Atomic fluorescence spectrometry (AFS) is based on the excitation of gaseous atoms by optical radiation of suitable wavelength (frequency) and the measurement of the resultant fluorescence radiation. Atomic fluorescence is, thus, in principle the opposite process to atomic absorption. Each atom has a characteristic fluorescence spectrum. The wavelength of the fluorescence line may be the same, greater, or smaller than the wavelength of the excitation line. 

Principles of Chemical and Biological Sensors. Edited by Dermot Diamond Pestidde Residue in Foods Methods, Technologies, and Regulations. By W. George Fong, H. Anson Moye, James N. Seiber, and John P. Toth X-Ray Fluorescence Spectrometry. Second Edition. By Ron Jenkins Statistical Methods in Analytical Chemistry. Second Edition. By Peter C. Meier and Richard E. Zild... 

See also Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Principles and Instrumentation. Atomic Fluorescence Spectrometry. Gas Chromatography Pyrolysis Mass Spectrometry. Liquid Chromatography Normal Phase Reversed Phase Size-Exclusion. Polarography Inorganic Applications Organic Applications. Polymers Synthetic. Thin-Layer Chromatography Overview. Voltammetry Organic Compounds. 

See also Atomic Absorption Spectrometry Principles and Instrumentation. Atomic Emission Spectrometry Principles and Instrumentation. Atomic Fluorescence Spectrometry. 

Potts PJ (1987) X-ray fluorescence analysis Principles and practice of wavelength dispersive spectrometry. In Potts PJ (Ed.) A Handbook of Silicate Rock Analysis, ch. 8. Glasgow Blackie. 

Basically, the I content in the purified iodine fraction can be measured by different techniques. Due to the low specific activity of this long-lived radionuclide, direct 3 , y and X-ray measurement techniques show only a moderate detection capability better detection limits can be obtained by determination of the I mass present in the sample. Here, laser-induced fluorescence spectrometry offers in principle favorable results however, when this technique is applied, the difficulties associated with the preparation of the h chemical species at very low iodine concentrations have to be taken into consideration. The most sensitive I determination technique is neutron activation analysis, which leads to the formation of the... 

Principles and Characteristics The analytical capabilities of the conventional fluorescence (CF) technique (c/r. Chp. 1.4.2) are enhanced by the use of lasers as excitation sources. These allow precise activation of fluorophores with finely tuned laser-induced emission. The laser provides a very selective means of populating excited states and the study of the spectra of radiation emitted as these states decay is generally known as laser-induced fluorescence (LIF, either atomic or molecular fluorescence) [105] or laser-excited atomic fluorescence spectrometry (LEAFS). In LIF an absorption spectrum is obtained by measuring the excitation spectrum for creating fluorescing excited state... 

Peptide analysis is an important field of application for which several approaches exist, all based on the same functional principle of enzymatic cleavage as initial step followed by classical fragment analysis. Lab-on-a-chip approaches aim at real-time high-throughput analysis of peptides with minimal possible amounts of sample substance. The peptides are handled in aqueous solution as they are funneled to the enzyme immobilized onto the micro-channel wall. The fission products are then detected by classical methods [25-28] such as GC, LC-MS, MS/MS, MALDI-TOF, ESI-TOF, CE, UV-Vis, and fluorescence spectrometry. 

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