electrochromatography

Electrochromatography is a separation technique that combines principles of electrophoresis and chromatography. In this method, an electric field is applied to a stationary phase that is also saturated with a mobile phase, typically a liquid. This electric field causes charged species to migrate through the stationary phase at different rates, in addition to the partitioning differences that are characteristic of chromatography.

The fundamental principle involves the interplay of electroosmotic flow, electrophoretic mobility, and chromatographic interactions. Electroosmotic flow is the bulk movement of the mobile phase caused by the electric field interacting with charged surfaces of the stationary phase. Electrophoretic mobility refers to the movement of charged analytes in response to the electric field, influenced by their charge and size. Chromatographic interactions occur between the analytes and the stationary phase, leading to differential retention.

Electrochromatography can be performed in various formats, including capillary electrochromatography (CEC), where the stationary phase is packed into a capillary tube, and planar electrochromatography, which utilizes flat surfaces. The separation efficiency in electrochromatography can be very high, often surpassing that of traditional HPLC and electrophoresis due to the combined separation mechanisms. It is particularly useful for separating neutral and charged species simultaneously, as well as isomers and closely related compounds. Applications are found in fields such as pharmaceutical analysis, environmental monitoring, and biochemistry.