Separation principle, capillary electrophoresis

F. BressoUe, M. Audran, T.-N. Pham, and J-J. Vallon, Cyclodextrins and enantiomeric separations of drugs by liquid chromatography and capillary electrophoresis Basic principles and new developments, J. Chro-matogr. B 657 303 (1996). 

Capillary Electrophoresis. Capillary electrophoresis (ce) is an analytical technique that can achieve rapid high resolution separation of water-soluble components present in small sample volumes. The separations are generally based on the principle of electrically driven ions in solution. Selectivity can be varied by the alteration of pH, ionic strength, electrolyte composition, or by incorporation of additives. Typical examples of additives include organic solvents, surfactants (qv), and complexation agents (see Chelating agents). 

Some coupled systems allow measurement of the main N and P forms (nitrate, ammonia and orthophosphates) [22,27,29], among which is a system based on membrane technology in combination with semi-micro continuous-flow analysis (pCFA) with classical colorimetry. With the same principle (classical colorimetry), another system [30] proposes the measurement of phosphate, iron and sulphate by flow-injection analysis (FIA). These systems are derived from laboratory procedures, as in a recent work [31] where capillary electrophoresis (CE) was used for the separation of inorganic and organic ions from waters in a pulp and paper process. Chloride, thiosulphate, sulphate, oxalate,... 

In CZE, the capillary, inlet reservoir, and outlet reservoir are filled with the same electrolyte solution. This solution is variously termed background electrolyte, analysis buffer, or run buffer. In CZE, the sample is injected at the inlet end of the capillary, and components migrate toward the detection point according to their mass-to-charge ratio by the electrophoretic mobility and separations principles outlined in the preceding text. It is the simplest form of CE and the most widely used, particularly for protein separations. CZE is described in Capillary Zone Electrophoresis. ... 

Electrophoresis has been used for a long time as one of the most important separation principles in analytical biochemistry. In particular, it has been applied to the separation of DNA and DNA components. Electrophoretical techniques have predominated in this field for decades and will continue to do so in the future. The advent of capillary electrophoresis (CE) has boosted the development of electrophoretic techniques, because it opened access to higher sensitivity, better resolution, and greater speed of separation (1-3). 

G Gubitz, MG Schmid. Recent progress in chiral separation principles in capillary electrophoresis. Electrophoresis 21 4112-4135, 2000. 

The electrophoretic separation technique is based on the principle that, under the influence of an applied potential field, different species in solution will migrate at different velocities from one another. When an external electric field is applied to a solution of charged species, each ion moves toward the electrode of opposite charge. The velocities of the migrating species depend not only on the electric field, but also on the shapes of the species and their environmment. Historically, electrophoresis has been performed on a support medium such as a semisolid slab gel or in nongel support media such as paper or cellulose acetate. The support media provide the physical support and mechanical stability for the fluidic buffer system. Capillary electrophoresis (CE) has emerged as an alternative form of electrophoresis, where the capillary wall provides the mechanical stability for the carrier electrolyte. Capillary electrophoresis is the collective term which incorporates all of the electrophoretic modes that are performed within a capillary. 

The technique has been named immunoaffinity electrochromatography (1ACEC) [180]. In principle, the solute diluted in a large volume is applied to a capillary column packed with a support containing anti-solute IgG. The solute is selectively extracted by the immunoaffinity column, and the bound analyte is eluted and separated further (if desired) by capillary electrophoresis. 

Capillary electrophoresis combines the separation principles of gel electrophoresis with the throughput and detection methods of HPLC. It overcomes the disadvantages of slab gel electrophoresis, including slow and labor intensive procedures and the difficulty and inaccuracies of quantitation. CE is... 

The separation principle in capillary gel electrophoresis (CGE) is the same as that of slab gel electrophoresis. Most often CGE is used in a denaturing mode with the incorporation of SDS and is referred to as SDS-CGE. As such, separation is based on the protein s molecular mass and, due to the sieving mechanism of the gel, smaller proteins migrate past the detector first. The use of a gel material and SDS decreases the EOF and eliminates protein adsorption to the capillary walls further ensuring that migration is based on molecular mass. This precludes the need for additives and coated capillaries. 

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