Capillary Electrochromatography

In conventional liquid chromatography, the flow of eluent is generated by the application of a pressure gradient, which is usually provided by means of a high-pressure mechanical pump. However, under certain conditions, the mobile phase can be forced to migrate through the chromatographic medium by the application of an electric field. This phenomenon of electrically induced fluid flow is commonly referred to as electro-osmosis or electro-osmotic flow. Liquid chromatography making use of this effect, where the pump is substituted by a high-voltage power supply, has been given a number of descriptions, including chromatoendosmosis and electroendosmosis. However, the term electrochromatography has been adopted by authors of the most recent publications and accordingly will be the one used here. The use of an electrical field in liquid chromatography has been discussed by several workers (1 ,2 ). However, the first discussion since the advent of modern HPLC, proposing the use of electro-osmotic flow as an alternative to pressure driven flow was given by Pretorious and coworkers in 1974 (3 ).