Basic Concepts of Capillary Electrophoresis

Capillary electrophoresis is similar to chromatography in many respects, and most of the words used in chromatography are also found in CE. For example, resolution and efficiency are common to both techniques and are defined in a similar way. However, some of the terminology is different, as illustrated in Table 4.1. For example, in chromatography, a column in used to separate the analytes in electrophoresis, a capillary is used. In chromatography a pump is used to propel the sample through the column in electrophoresis, there is no external pumping system, and the 

Carrier electrolyte or buffer Eluent or mobile phase 

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Another recent development is the advent of pulse amperometry in which the potential is repeatedly pulsed between two (or more) values. The current at each potential or the difference between these two currents ( differential pulse amperometry ) can be used to advantage for a number of applications. Similar advantages can result from the simultaneous monitoring of two (or more) electrodes poised at different potentials. In the remainder of this chapter it will be shown how the basic concepts of amperometry can be applied to various liquid chromatography detectors. There is not one universal electrochemical detector for liquid chromatography, but, rather, a family of different devices that have advantages for particular applications. Electrochemical detection has also been employed with flow injection analysis (where there is no chromatographic separation), in capillary electrophoresis, and in continuous-flow sensors. 

This chapter introduces the basic concepts and principles of capillary electrophoresis (CE), presenting some background on electrophoresis and capillary electrophesis and describing the components of the system. The two main types of CE, capillary zone and micellar electrokinetic electrophoresis, are described, and a selection strategy, based on the two types of separation, electrophoretic migration and electroosmosis, is presented. 

Capillary electrophoresis (CE) is a separation technique that employs the basic concepts and separation mechanism of conventional electrophoresis in a capillary format. The core of the CE system is in fact a capillary, normally in fused silica, with an internal diameter of 50-100 pm that is filled with the buffer solution (defined as the background electrolyte (BGE)) to be used for separation of the charged molecules. 

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