Conductivity detection in capillary electrophoresis

Abstract

Among electrochemical detection methods in capillary electrophoresis, conductometric methods are of specific interest for the determination of inorganic species. This is due to the fact that inorganic ions exhibit a high equivalent conductivity which corresponds to the analytical signal in conductivity detection. Indirect optical absorption methods, which are widely used in capillary electrophoretic ion analyses, become less sensitive with smaller capillary dimensions and thus have disadvantages in electrokinetic chip separation technologies. Conductivity detection for capillary electrophoresis is performed either through galvanic contact or in a contactless mode. Techniques using a galvanic contact of the sample ions with the measuring electrode are performed either on-capillary without decoupling of the separation high voltage, or off-capillary after grounding the separation voltage in order to avoid interferences. This technology is specifically important when a suppressor is used prior to detection. Most contactless methods use oscillometric techniques in order to obtain the analytical signal. This review discusses the theoretical and instrumental background of conductivity detection in capillary electrophoresis and reports on recent aspects and applications using conductometric detection methods for capillary zone electrophoresis.