Capillary Zone Electrophoresis with Electrochemical Detection

A system for interfacing electrochemical detection as well as other “off-column” detectors with capillary zone electrophoresis Is demonstrated. This system couples two pieces of column together with a section of porous glass capillary thus forming a Joint that Is electrically conductive. The Joint Is immersed in a buffer reservoir along with the ground electrode In order to allow the separation potential to be applied across only the first section of capillary. The strong electroosmotic flow generated in the first section of capillary serves to force solvent and analyte zones past the Joint and through the second section of capillary to the detector. This configuration effectively separates the detector from the high applied voltage via the resistance of the detection capillary. We have used this system to successfully perform electrochemical detection with capillary zone electrophoresis and have obtained separation efficiencies on the order of 180 000 theoretical plates for the separation of catechol from catechol-amines. Preliminary data Indicate that a back pressure created by solvent within the second capillary is a significant contributor to zone broadening. However, this effect is minimized when a short second capillary segment Is employed.