Optical methods of analysis

Optical Methods of Analysis. Optical methods of analysis of reaction systems are very convenient where they can be applied. The optical properties which characterize the system may be the absorption at one or more particular wavelengths (in the ultraviolet, visible infrared, or microwave region), the refractive index of the mixture, the optical rotation of one or more species, the light-scattering properties of large molecules, or the fluorescent emission of one or more of the substances present. 

Any of these methods may be used in conjunction with a static or flow system or else a flow system in which the reaction mixture is cycled to the optical measuring system and returned to the original reaction vessel. 

Each requires a very careful calibration of the system in order to obtain the composition from the measured optical property. If only one component is analyzed, then it is essential to show that its optical property is uniquely related to its concentration and is not dependent upon the other substances present. With the exception of optical rotation and refractive index, most of the optical methods do not give better than a 1 per cent accuracy under normal operating conditions, and generally the accuracy is much less.  

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Optical methods of analysis are dependent either upon (i) measurement of the amount of radiant energy of a particular wavelength absorbed by the sample, or (ii) the emission of radiant energy and measurement of the amount of energy of a particular wavelength emitted. Absorption methods are usually classified according to the wavelength involved as (a) visible spectrophotometry (colorimetry), (b) ultraviolet spectrophotometry, and (e) infrared spectrophotometry. 

Koldioff, [,M. P.J. Elving, and E.J. Meehan Optical Methods of Analysis, Vol. 8, Treatise on Analytical Chemistry, Part 1, John Wiley Sons, Inc., New York, NY, 1986. 

Olsen, E.D. Modem Optical Methods of Analysis, McGraw-Hill New York, NY, 1975. 

To relate the wettability changes more firmly to the photooxidation processes and products, a detailed study was carried out with polystyrene. This polymer was selected because the formation of oxidation products in the hydrocarbon surface gave rise to large changes in wettability and because these products would be readily accessible to optical methods of analysis. The ultraviolet absorption spectrum of polystyrene shows a sharp cut-off, and the extinction coefficients for the radiation absorbed are sufficiently high that almost all of the photochemical reaction should be confined to the surface layers. 

With respect to other major literature on or related to XRE, are chapters in various analytical series and individual books. Two chapters are in the first edition of the famous Treatise on Analytical Chemistry. Comprehensive coverage of X-ray methods absorption, diffraction, and emission is provided by Liebhafsky et al. (1964) in a 90-page chapter in the section on Optical methods of analysis (E. J. Meehan, section advisor). This is immediately followed by the chapter by Wittry (1964) on X-ray microanalysis by means of electron probes. Chapters on relevant topics appearing in the other well known series on analytical chemistry. Comprehensive Analytical Chemistry, are by Beretka (1975) (Analytical applications of electron microscopy) with a brief mention of the XRF-based technique electron probe... 

Liebhaesky HA, Peeieeee HG and Winslow EH (1964) X-ray methods absorption, diffraction, and emission. In KolthofFiM, Elving PJ and Sandell EB, eds. Treatise on analytical chemistry Part I (Theory and practice), Vol 5, section D-3, Optical methods of analysis (Meehan EJ, section advisor), pp. 3079-3172. John Wiley Sons, New York. 

Meehan, E.J. Optical Methods of Analysis. Treatise on Analytical Chemistry, 2nd ed. John Wiley and Sons, Ltd. Chichester, 1981. 

Meehan, E.J. Optical methods of analysis. In Treatise on Analytical Chemistry, Living, P. J., Meehan,... 

Olsen ED (1975) Modern Optical Methods of Analysis. New York McGraw Hill. 

F. Alison, Magneto-Optic Method of Analysis as a New Research Tool, Ind. Eng. Chem. Anal. Ed. 1932, 4, 9—12... 

The optical methods of analysis, as well as those based on X-ray transitions (Chap. 5) are of great interest for determinations of the presence and concentration of a very large number of substances. The presence of chemical elements can be determined and molecular identification can also be made. Molecular analysis can be performed by IR absorption spectroscopy and also by XPS (Chap.5) and NMR (Chap.7). We will briefly describe some applications of optical analysis methods. 

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