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 detec tion (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 held on the detection can be practically eliminated, without usin g a decoupler, by positioning the reference electrode sufficiently close to the working electrode. In the present study, this was demonstrated by usin g 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 a nd reference electrodes, respectively. The short distance (i.e., 10 mum) be tween the working and reference electrode ensured that both of the electrod es were very similarly affected by the presence of the CE electric field. W ith 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.