Capillary-Electromigration Separation Techniques

Capillary-electromigration separation techniques are a family of separation methods carried out in empty, coated or packed capillary columns with electrolyte solutions as the mobile phase. An electric field is resonsible for driving the sample and mobile phase through the column by processes dependent on electrophoresis and electroosmosis. This common arrangement allows a similar instrument platform to service all capillary-electromigration separation techniques with only minor modifications for specific applications. These methods only recently entered analytical laboratories, although in a planar format they have a long history of use in biochemical and chnical laboratories [1-5]. 

From the beginning of free solution electrophoresis, band broadening from thermal effects was foreseen as the main problem restricting its development [6]. The energy generated as heat by application of an electric field to an electrolyte solution in a column raises the solution temperature, but more critically, results in a radial 

Capillary-electromigration separation techniques are said to reduce method development time, to reduce operating costs and solvent consumption, provide higher efficiency, and are easier to interface to some types of detectors compared with column hquid chro- 

Application of an electric field to an ion in solution causes the ion to move with a constant velocity that depends on the field strength, temperature and characteristic properties of the ion and electrolyte solution. The electrostatic force accelerating the ion (F = qE) is opposed by viscous forces in the solution restricting its movement. For a spherical particle the viscous force is given by Stokes law (F = firttirvep). After a short 

Eor a simpler comparison of experimental data the electrophoretic mobility, Xep, defined as the analyte electrophoretic velocity at unit field strength, is generally used. 

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FIGURE 6.3 Scheme of a basic instrument for capillary electromigration separation techniques. 

Poole, C.E. (2003) Chapter 8 Capillary-electromigration separation techniques, in The Essence of Chromatography, Elsevier, Amsterdam, pp. 619-717. 

Modem instruments for capillary-electromigration separation techniques are characterized by a high level of automation, computer control and safety features [8-13,420-422]. 

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