Fluorescence principles and measurement

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). 

Principle The measurements of fluorescence spectra or /and fluorescence intensity by microspectrofluorimeters, which are a luminescent microscope combined with a multiplayer and a recorder (or a computer). 

Lubbers DW, Opitz N, Speiser PP, Bisson HJ (1977) Nanoencapsulated fluorescence indicator molecules measuring pH and p02 down to submicroscopical regions on the basis of the optode principle. Z Naturforsch 32 133-134... 

Abstract Flow cytometry is a technique for rapidly examining multiple characteristics of individual cells, by recording fluorescence signals emitted from cell-associated reporter molecules, and measuring cellular light scattering properties. This chapter introduces the principles and practice of flow cytometry, and reviews examples from the literature that highlight applications of this experimental tool in the neurosciences. The chapter concludes with protocols for three basic procedures that illustrate some practical aspects of analytical flow cytometry. 

Polarity Variation in Sulfonate Micelles. Other workers have established a correlation between the fluorescence lifetime of pyrene in solution and the polarity of the solvent medium (9). Polar media quench the excited electronic state of pyrene and hence shorten its fluorescence lifetime. We applied this principle to measure the polarity variation within the micelles of sulfonates A and B. 

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... 

---