Laser spectroscopy, analytical method Applications

Fluorescence spectroscopy and its applications to the physical and life sciences have evolved rapidly during the past decade. The increased interest in fluorescence appears to be due to advances in time resolution, methods of data analysis and improved instrumentation. With these advances, it is now practical to perform time-resolved measurements with enough resolution to compare the results with the structural and dynamic features of macromolecules, to probe the structures of proteins, membranes, and nucleic acids, and to acquire two-dimensional microscopic images of chemical or protein distributions in cell cultures. Advances in laser and detector technology have also resulted in renewed interest in fluorescence for clinical and analytical chemistry. 

Trace Analysis Spectroscopic Methods for Elements. Edited by J. D.Winefordner Contamination Control in Trace Element Analysis. By Morris Zief and James W. Mitchell Analytical Applications of NMR. By D. E. Leyden and R. H. Cox Measurement of Dissolved Oxygen. By Michael L. Hitchman Analytical Laser Spectroscopy. Edited by Nicolo Omenetto... 

The Nickel Producers Environmental Research Association (NiPERA) is sponsoring research on the application of inductively coupled plasma-mass spectroscopy (ICP-MS) to isotopic analysis of nickel in biological samples, on the development of sampling instrumentation for assessing workers exposure to nickel in the nickel industry, and on methods for utilizing newly developed analytical methods, such as laser beam ionization mass spectrometry, for the identification and speciation of nickel compounds in powders and dusts with particular reference to nickel refining. 

Future Trends. Methods of laser cooling and trapping are emerging as of the mid-1990s that have potential new analytical uses. Many of the analytical laser spectroscopies discussed herein were first employed for precise physical measurements in basic research. Applications to analytical chemistry occurred as secondary developments from 10 to 15 years later. 

Nonlinear vibrational spectroscopy provides accessibility to a range of vibrational information that is hardly obtainable from conventional linear spectroscopy. Recent progress in the pulsed laser technology has made the nonlinear Raman effect a widely applicable analytical method. In this chapter, two types of nonlinear Raman techniques, hyper-Raman scattering (HRS) spectroscopy and time-frequency two-dimensional broadband coherent anti-Stokes Raman scattering (2D-CARS) spectroscopy, are applied for characterizing carbon nanomaterials. The former is used as an alternative for IR spectroscopy. The latter is useful for studying dynamics of nanomaterials. 

As it is common in the Raman scattering process to observe Raman band intensities of ca. 10 of the incident photons (UV, VIS, NIR) provided by a monochromatic laser source, Raman spectroscopy is an inherently insensitive analytical method that usually requires molecular concentrations of >0.01 M. Raman spectroscopy probably represents the single largest application of laser spectroscopy in industrial analysis and is being used in industry only as from the 1980s for the analysis of a wide range of materials, mainly solids. Raman spectroscopy is... 

This chapter is only concerned with spectroscopic techniques applicable to polymer/additive analysis insofar as not reported under the specific headings of laser ablation (c/r. Chp. 3.2) or laser pyrolysis (c/r. Chp. 3.5). Laser spectroscopy, which is no substitution of conventional methods but a valuable addition of the analytical toolbox, has extensively been reviewed [1,98]. Chemical spectroscopy with lasers [9] and applications of laser spectroscopy were described in monographs [1,3,99]. 

The simplicity and robustness of the method makes it well suited to a number of practical analytical applications, such as sensitive noninvasive in vivo disease diagnosis, security screening and the quality control of pharmaceutical tablets. The concept is also potentially applicable to fluorescence spectroscopy, NIR tomography of turbid media and other general applications, where the enhanced coupling of laser radiation into a turbid medium is beneficial an example is the case of photodynamic therapy in cancer treatment of subsurface tissues. 

Nonlinear techniques have been used to overeome some of the drawbacks of conventional Raman spectroscopy, particularly its low dficienev, its limitation to the visible and near-ultraviolet regions, and its susceptibility to interference from fluorescence. A major disadvantage of nonlinear methods is that they lend to be analyte specific and often require several different tunable lasers to be applicable lo diverse species. I o dale, none of the nonlinear methods has found widespread application among nonspccialisls. However, many of these methods have shown considerable promise. As less expensive and more routinely useful lasers become available, nonlinear Raman methods, particu-larlv CARS, should become more widely used. 

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