Tag Archives: electrophoresis

Capillary Electrochromatography

Another approach to separating neutral species is capillary electrochromatography, CEC. In CEC the capillary tubing is packed with 1.5–3 μm particles coated with a bonded stationary phase. Neutral species separate based on their ability to partition between the stationary phase … Continue reading

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Micellar Electrokinetic Capillary Chromatography

One limitation to capillary electrophoresis is its inability to separate neutral species. Micellar electrokinetic capillary chromatography, or MEKC, overcomes this limitation by adding a surfactant, such as sodium dodecylsulfate (a) to the buffer solution. Sodium dodecylsulfate, or SDS, has a … Continue reading

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Reversed Migration in Capillary Electrophoresis

We can reverse the direction of electroosmotic flow in capillary electrophoresis by adding an alkylammonium salt to the buffer solution. As shown in (b), the positively charged end of the alkyl ammonium ions bind to the negatively charged silanate ions … Continue reading

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Stacking of Cations and Anions in Capillary Electrophoresis

When a analyte’s concentration is too small to detect reliably, it may be possible to introduce it in a manner that increases its concentration in the capillary tube. This method of injection is called stacking. Stacking is accomplished by placing … Continue reading

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UV/Vis Detectors for Capillary Electrophoresis

Most of the detectors used in HPLC also find use in capillary electrophoresis. Among the more common detectors are those based on the absorption of UV/Vis radiation, fluorescence, conductivity, amperometry, and mass spectrometry. Whenever possible, detection is done “on-column” before … Continue reading

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Instrumentation for Capillary Electrophoresis

The basic instrumentation for capillary electrophoresis is shown here and includes a power supply for applying the electric field, anode and cathode compartments containing reservoirs of the buffer solution, a sample vial containing the sample, the capillary tube, and a … Continue reading

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Total Mobility of Solutes in Capillary Electrophoresis

In capillary electrophoresis we inject the sample into a buffered solution retained within a capillary tube. When an electric field is applied across the capillary tube, the sample’s components migrate as the result of two types of action: electrophoretic mobility, … Continue reading

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Electroosmotic Flow

When an electrical field is applied to a capillary filled with an aqueous buffer we expect the buffer’s ions to migrate in response to their electrophoretic mobility. Because the solvent, H2O, is neutral we might reasonably expect it to remain … Continue reading

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Electrophoretic Separation

In chromatography, a separation occurs because there is a difference in the equilibrium partitioning of solutes between the mobile phase and the stationary phase. Equilibrium partitioning, however, is not the only basis for effecting a separation. In an electrophoretic separation, … Continue reading

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