Elimination of nigh-voltage field effects in end column electrochemical detection in capillary electrophoresis by use of on-chip microband electrodes

The influence of the separation voltage on end column electrochemical detection (EC) in capillary electrophoresis (CE) has been investigated using an electrochemical detector chip based on an array of microband electrodes. It is shown, both theoretically and experimentally, that the effect of the CE electric field on the detection can be practically eliminated, without using a decoupler, by positioning the reference electrode sufficiently close to the working electrode. In the present study, this was demonstrated by using an experimental setup in which neighboring microband electrodes on a chip, positioned 30 pm from the end of the CE capillary, were used as working and reference electrodes, respectively. The short distance (i.e., 10 mum) between the working and reference electrode ensured that both of the electrodes were very similarly affected by the presence of the CE electric field. With this experimental setup, no significant influence of the CE voltage on the peak potentials for gold oxide reduction could be seen for CE voltages up to +30 kV, The detector noise level was also found to be reduced.