CAPILLARY ELECTROPHORESIS WITH ELECTROCHEMICAL DETECTION EMPLOYING AN ON-COLUMN NAFION JOINT

The construction and evaluation of an on-column joint utilizing Nafion tubing for the isolation of the electrical circuit from the detection end of a capillary zone electrophoresis system is described. The joint enables electrochemical detection to be performed without adverse effects from the applied high voltage. The joint is both simple to construct and durable. The electrochemical detector employing a carbon fiber working electrode exhibited high coulometric efficiencies and a detection limit of 6.10(-9) M or 34.8 amol for hydroquinone. A high efficiency, of the order of 185 000 theoretical plates, was achieved for this compound. This system was evaluated for the detection of phenolic acids in apple juice and for the determination of naphthalene-2,3-dicarboxaldehyde derivatized amino acids in a brain homogenate. The use of voltammetry as a method of compound verification was also demonstrated.