Capillary isoelectric focusing review

In spite of all these clear advantages, capillary isoelectric focusing is still not used as a routine method in bioanalysis, although more and more papers show important applications. Study of the proteome combined with microchip technology may, however, cause sudden progress in this innovative technique. In the past decade several reviews have appeared about CIEF separations [5-17]. This chapter summarizes the theory and the newest innovations, as well as applications of CIEF. 

Several modes of CE have been described in the literature over past decade [6, 7], The most common are open tubular or capillary zone electrophoresis (CZE), micellar electrokinetic chromatography (MEKC), microemulsion elec-trokinetic chromatography (MEEKC), capillary electrochromatograpy (CEC), capillary gel electrophoresis, capillary isoelectric focusing and capillary iso-tachophoresis. Three recent reviews by Watzig [113], Tagliaro etal. [114] and Riekkola etal. [115] summarise the current method development options available to manipulate selectivity. In pharmaceutical analysis, CZE, MEKC, MEEKC and CEC are commonly used. 

Capillary isoelectric focusing (CIEF) is designed to separate solutes based on their p/, the pH where they are electrically neutral. Because solutes do not migrate when they are neutral, the mobilization step distinguishes CIEF from other capillary electrophoretic techniques. This entry reviews the basis for CIEF including pH gradient formation, mobilization techniques, additives, and applications. 

Although CE instruments are not well designed for CIEF, many variants can be separated better by this technique. In addition to the common variants, G Philadelphia, A2, and Bart s can all be separated by CIEF [46-48]. The separation by CIEF compares well with gel isoelectric focusing and with HPLC. The variants have also been analyzed by both CE and CIEF equipped with special absorption imaging detectors. These types of detection devices eliminate the extra steps needed to move the peaks, after the focusing step, to the detector and can simultaneously detect several capillaries with better precision and faster results than CE instruments. HB A2, which is increased in P-thal, is better quantified by CE compared with AG electrophoresis [44]. Hemoglobin analysis by CE has been reviewed recently [49-51]. 

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