Various electrophoretic techniques

Capillary electrophoresis (CE) separates sample components within a capillary tube under the effect of an electric field employed across the two ends of the capillary. The different 

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The good separation capacity, low solvent consumption, rapidity and relative simplicity of various electrophoretic techniques have also been exploited in the separation and quantitative determination of synthetic dyes. 

Various support media may be employed in electrophoretic techniques. Separation on agarose, acrylamide, and paper is influenced not only by electrophoretic mobiUty, but also by sieving of the samples through the polymer mesh. The finer the weave of selected matrix, the slower a molecule travels. Therefore, molecular weight or molecular length, as well as charge, can influence the rate of migration. 

The separation methods routinely employed in the laboratory include the various chromatographic and electrophoretic techniques, whose selectivity is continually being increased by the introduction of new adsorbents, e.g. with chemically modified surfaces (Fig. 1). 

Because of their high separation capacity, short analysis time, low reagent consumption and simplicity, various electrophoretic methods have found application in the separation and quantitative determination of anthocyanins in various complex matrices [267].The different techniques used for the measurement of anthocyanins in beverages [268], the application of capillary electrophoresis (CE) for the analysis of natural food pigments [269], the use of CE for the determination of anthocyanins in foods [270] and in medicinal plants [271] have been previously reviewed. 

An overview of the principles of chiral separations in CE and HPLC is given in the first part of this chapter. The second part is dedicated to an overview of chiral separation with CE. The popularity of electrophoretic techniques has grown spectacularly in recent years, mainly due to their exceptional performances in the chiral field. Various selectors can easily... 

Because of the use of various electrolyte systems, pH gradients, and not least an electric field, some complexes would not survive the separation. It is therefore necessary that the species to be separated are both thermodynamically and kineti-cally stable. Recently, Bocek and Foret have reviewed the application of isotachophoresis to the separation of inorganic species. This technique appears to be well-suited for the study of the distribution of metabolites of metal-containing drugs in body fluids. A survey of the application of electrophoretic techniques to biological materials can be found in the book edited by Deyl... 

Urinary GAGs are precipitated before TLC is performed. Separation of the GAGs is achieved by exploiting the different solubility of their calcium salts in various concentrations of ethanol [18, 35, 42]. TLC can provide an inexpensive alternative to electrophoretic techniques, especially when such equipment is not available. 

The relationship between the various tissue alkaline phosphatases has been under discussion for many years (24). Bodansky established that inhibition by bile acids could be used to distinguish between intestinal and bone or kidney isoenzymes (25). The organ-specific behavior of rat tissue phosphatases toward a variety of compounds was investigated by Fishman (26). Of particular importance was the observation that l-phenylalanine is a stereospecific inhibitor for the intestinal isoenzyme (27). Immunochemical (28, 29) and electrophoretic techniques (30, 31) have shown that there are also physical differences between the tissue phosphatases. It is not yet clear what the precise nature of these differences is (32), although in part it results from a variability in sialic acid content. 

Among the electrophoretic methods of chiral resolution, various forms of capillary electrophoresis such as capillary zone electrophoresis (CZE), capillary isotachophoresis (CIF), capillary gel electrophoresis (CGE), capillary isoelectric focusing (CIEF), affinity capillary electrophoresis (ACE), and separation on microchips have been used. However, in contrast to others, the CZE model has been used frequently for this purpose [44]. On the other hand, drawbacks associated with the electrophoretic technique due to lack of development of modem chiral phases have limited the application of these methods. Moreover, the electrophoretic techniques cannot be used at the preparative scale, which represents an urgent need of chiral separation science. 

A range of electrophoretic techniques use the capillary prindple capillary zone electrophoresis (CZE), capillary isotachophoresis (CITP), capillary gel electrophoresis (CGE), capillary isoelectric focusing (CIEF) and micellar electrokinetic capillary chromatography (MECC). Some of these techniques, particularly CZE and CGE, have already established themselves as important analytical tools others, notably MECC, may open new approaches in analytical biochemistry. Table 4-11 summarises the areas of application of the various techniques in what follows we shall focus on CZE, CGE and MECC. 

Various electrophoretic separation principles can be combined, e.g. Isotachophoresis followed by zone-electrophoresis. Such an equipment is produced by the Institute of Radio-ecology and Applied Nuclear Techniques (Column-coupling Isotachophoretic analyser ZKl-001 Pzo Kovo, J2uikovcova 2, 17088 Praha, CSSR). 

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