Conducting polymer and oligomer micro-electrodes for the potentiometric detection of anions in capillary electrophoresis

A conducting polymer (polypyrrole (PPy)) electrode and a conducting oligome r (CO) (phenylene vinylene trimer) electrode were used in a potentiometric detector for capillary electrophoresis (CE). The coated-wire electrodes had diameters of 258 mu m A home-made capillary + electrode holder was describ ed which allowed an easy electrode alignment. Mixtures of low molecular wei ght carboxylic acids and inorganic anions were separated in a co-electroosm otic mode. They could be detected in injected concentrations down to 5 x 10 (-6) M. The interelectrode variation was 7.2%, and the electrode materials were used for 2 months without loss of sensitivity. The addition of a quate rnary ammonium ion to the buffer electrolyte as an electroosmotic flow (EOF ) modifier was compatible with the electrode materials used. A theoretical model is presented to describe the behaviour of the coated-wire potentiomet ric detectors. The PPy electrode is very suitable for use in miniaturised s eparation systems as PPy can be deposited electrochemically. (C) 1999 Elsev ier Science B.V. All rights reserved.