Electrochemical detection with microelectrodes in capillary flow systems

A novel electrochemical cell for capillary electrophoresis with end-column amperometric detection is described. A platinum microdisk electrode (dpt = 25 μm) facing the capillary outlet served as sensing electrode. The problem of interference of the high voltage electrical field with the microelectrode circuit has been solved by the construction of a glass sleeve/Nafion joint for 100 μm i.d. capillaries. With 25 μm i.d. capillaries end-column detection could be performed without the use of an electrical-field decoupler arrangement. The analytical performance of the detector was characterized applying capillary zone electrophoresis and micellar electrokinetic capillary chromatography to separate various ferrocene derivatives. In addition, the same detector cell configuration has been used for amperometric detection in conjunction with capillary flow injection analysis.