Principle and Applications

When the potential of the OTE is stepped to a value such that reaction (2.16) proceeds at a diffusion-controlled rate, the time-dependent absorbance of R is given by 

Spectroelectrochemical experiments can be used to probe various adsorption and desorption processes. In particular, changes in the absorbance accrue from such processes can be probed utilizing the large ratio of surface area to solution volume of OTEs with long optical pathlength (30). Additional information on such processes can be attained from the Raman spectroelectrochemical experiments described below. 

In addition to transmission experiments, it is possible to use more sensitive reflectance protocols. In particular, in internal reflectance spectroscopy (IRS) the lightbeam is introduced to the electrode at an angle, and the spectrum are recorded from the reflected beam at the solid-solution interface. Prisms are used to let the radiation enter and leave. Besides its higher sensitivity, IRS is less prone to solution resistance effects. 

Infrared spectroelectrochemical methods, particularly those based on Fourier transform infrared (FTIR), can provide structural information that 

UV-vis absorbance techniques do not. FTIR spectroelectrochemicstry has thus been fruitful in the characterization of reactions occurring on electrode surfaces. The technique requires very thin cells to overcome solvent absorption problems. 

FIGURE 2-11 Spectra for a series of applied potentials (mV vs. Ag/AgCl) during thin-layer spectroelectrochemical experiment on 1.04 x 10 3 M [Tc(III)(dmpe)2Br2]+. Medium is dimethylformamide containing 0.5 M TEAP = tetraethylammonium perchlorate. (Reproduced with permission from reference 27.) 

FIGURE 2-12 Plot of dA/dt vs. E for 1.55 x 10 3 M methyl viologen at tin oxide optically transparent electrode, using scan rates of (A) 25, (B) 50, (C) 97.2 and (D) 265 mV s-1. (Reproduced with permission from reference 28.) 

Environment Canada, Environmental Technology Centre, Ottawa, ON, Canada, KIA OHS 

The technique was almost forgotten until it was resurrected in 1930 by Kuhn, Winterstein and Lederer. They separated the components of egg yolk by passing them through a glass column packed with calcium carbonate and identified two components lutein and zeaxanthin. 

During another experiment two isomers of a biologically important substance present in carrots, alpha- and beta-carotene, were characterised following a prebminary separation of carrot extracts on alumina. Chromatography was resuscitated  

It is only in 1958, when Stahl standardised the procedure and showed its wide applications, that thin layer chromatography (a derivative of paper chromatography) became a technique that is now used extensively and has become a classic Gas chromatography (GC) was first described in 1952 by Martin and James and, by the 1960 s, became the most sophisticated and used analytical technique for mixtures of gases and for volatile liquids and solids. This naturally led to its counterpart hquid chromatography or high-performance Liquid Chromatography (HPLC) preferred technique for separation of non-volatile or thermally unstable species. 

This chapter will discuss planar chromatography and column chromatography in general. The more advanced techniques such as gas chromatography (GC) and high performance liquid chromatography (HPLC) will be discussed extensively in subsequent chapters. 

Besides its widespread use for investigating the mechanism of redox processes, spectroelectrochemistry can be useftil for analytical purposes. In particular, the simultaneous profilmg of optical and electrochemical properties can enhance the overall selectivity of different sensing (30) and detection (31) apphcations. Such coupling of two modes of selectivity is facilitated by die judicious choice of the operatmg potential and wavelength. 

---

Prokhorenko P.P., Baev A.R., Grintsevich E.M. Physical Principles and Application of Magnetic Fluids to Ultrasonic Testing -. Journal of Magnetism and Magnetic Materials. -... 

R. J. Hunter, Zeta Potential in Colloid Seience Principles and Applications, Academic, Orlando, FL, 1981. 

D. F. Moore, Principles and Applications of D-ibology, Pergamon, New York, 1975. 

Ramsier R D and Yates J T Jr 1991 Electron-stimulated desorption principles and applications Surf. Sc/. Rep. 12 243... 

Rugar D, Mamin FI J, Guenther P, Lambert S E, Stern J E, McFadyen I and Yogi T 1990 Magnetic force microscopy general principles and application to longitudinal recording media J. Appl. Phys. 68 1169... 

Watt F, Grime G W and Fliiger A Principles and Applications of High-Energy Ion Microbeams (Bristoi institute of Physios)... 

Vickerman J C, Brown A and Reed N M (eds) 1989 Secondary Ion Mass Spectrometry, Principles and Applications (Oxford Clarendon)... 

Collman J P, Hegedus L S, Norton J R and Finke R G 1987 Principles and Applications of Organotransitlon Metal Chemistry (Mill Valley, CA University Soienoe)... 

Persson B N J 1997 Sliding Friction—Physical Principles and Applications (New York Springer)... 

S. S. Bhatnagar, K. M. Mathur, Physical Principles and Applications of Magnetochemistry. Macmillan, London, 1935. 

A.R. Leach, Molecular Modelling - Principles and Applications, 2nd edition, Pearson Education, Harlow, UK, 2001. 

A. R. Leach, Molecular Modelling Principles and Applications Longman, Essex (1996). P. Fulde, Electron Correlations in Molecules and Solids Third Enlarged Edition Springer,... 

A. R. Leach, Molecular Modelling Principles and Applications Longman, Essex (1996). 

J. P. CoIIman, L. S. Hegedus, J. R. Norton, and R. G. Finke, Principles and Applications of Organotransition Metal Chemistry, University Science Books, Mill Valley, CA, 1987. 

Palmieri, M. D. An Introduction to Supercritical Fluid Ghromatography. Part 1 Principles and Applications, ... 

Source Adapted from Valcarcel, M. tuque de Castro, M. D. Flow-Injection Analysis Principles and Applications. Ellis Norwood Chichester, England, 1987. 

Hoffmann, E. de, Charette, J., and Stroobant, V., Mass Spectrometry Principles and Applications, Wiley, Chichester, U.K., 1996. 

Eland, J. H. D. (1983) Photoelectron Spectroscopy. 2nd edn, Butterworth-Heinemann, London. Huffier, S. (2001) Photoelectron Spectroscopy Principles and Applications. 3rd edn. Springer, Berlin. Prince, K. C. (1995) Photoelectron Spectroscopy of Solids and Suifaces Synchrotron Radiation Techniques and Applications, World Scientific Publishing, Singapore. 

L. E. Murr, Electron and Ion Microscopy and Microanalysis Principles and Applications, 2nd ed.. Optical Engineering Vol. 29, Dekker, New York, 1991. 

G. M. Ritcey and A. W. Ashbrook, S olvent Extraction Principles and Applications to Process Metallurgy, Part I, Elsevier, Amsterdam, the Netherlands, 1984. 

M. E. Lines and A. M. Glass, Principles and Applications ofFerroelectrics and Related Materials, Clarendon, Oxford, UK, 1977. 

Pohland and Sratakis, Controlled Eandfill Management—Principles and Applications, Insight 91, Charleston, Oct. 1991. 

F. V. Lenel, Powder Metallurgy—Principles and Applications, Metal Powder Industries Federation, Princeton, N.J., 1980. 

W. Cheung, Microwaves Made Simple, Principles and Applications, Adtech Books Co. Ltd., London, 1985. 

---