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''Capillary electrochromatography'' (CEC) is a chromatographic technique in which the mobile phase is driven through the chromatographic bed by electroosmosis. Capillary electrochromatography is a combination of two analytical techniques, High performance liquid chromatography and capillary electrophoresis. Capillary electrophoresis aims to separate analytes on the basis of their mass to charge ratio by passing a high voltage across ends of a capillary tube, which is filled with the analyte. High performance liquid chromatography separates analytes by passing them, under high pressure, through a column filled with stationary phase. The interactions between the analytes and the stationary phase and mobile phase lead to the separation of the analytes. In capillary electrochromatography capillaries, packed with HPLC stationary phase, are subjected to a high voltage. Separation is achieved by electrophoretic migration of solutes and differential partitioning. ==Principle== Capillary electrochromatography (CEC) combines the principles used in HPLC and CE. The mobile phase is driven across the chromatographic bed using electroosmosis instead of pressure (as in HPLC). Electroosmosis is the motion of liquid induced by an applied potential across a porous material, capillary tube, membrane or any other fluid conduit. Electroosmotic flow is caused by the Coulomb force induced by an electric field on net mobile electric charge in a solution. Under alkaline conditions, the surface silanol groups of the fused silica will become ionised leading to a negatively charged surface. This surface will have a layer of positively charged ions in close proximity which are relatively immobilised. This layer of ions is called the Stern layer. The thickness of the double layer is given by the formula: δ= (εo RT / 2cF² )½ Where: εr = dielectric constant or relative permittivity of medium εo = permittivity of a vacuum R = universal gas constant T = absolute temperature c = molar concentration F = Faraday constant When an electric field is applied to the fluid (usually via electrodes placed at inlets and outlets), the net charge in the electrical double layer is induced to move by the resulting Coulomb force. The resulting flow is termed electroosmotic flow. In CEC positive ions of the electrolyte added along with the analyte accumulate in the electrical double layer of the particles of the column packing on application of an electric field they move towards the cathode and drag the liquid mobile phase with them. The relationship between the linear velocity u of the liquid in the capillary and the applied electric field is given by the Smoluchowski equation as follows: u = εrεoζEη Where: εr = Dielectric constant or relative permittivity of medium εo = Permittivity of a vacuum ζ = Potential across the Stern layer (Zeta Potential) E = Electric field strength η = Viscosity of the solvent Separation of components in CEC is based on interactions between the stationary phase and differential electrophoretic migration of solutes. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Capillary electrochromatography」の詳細全文を読む スポンサード リンク
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