PREPARATION OF MICROELECTRODES - COMPARISON OF POLISHING PROCEDURES BY STATISTICAL-ANALYSIS OF VOLTAMMETRIC DATA

Manual and instrumental procedures for polishing 1 and 6 mu m radius p latinum microdisc electrodes were compared by performing a statistical evaluation of three basic electrochemical signal characteristics meas ured from steady-state voltammmograms for oxidation of ferrocene in ac etonitrile. The three signal characteristics measured were the limitin g current I-lim, the half-wave potential E(1/2) and the (E(3/4) - E(1/ 4)) potential difference, where E(3/4) and E(1/4) are the potentials a t three quarters I-lim and one quarter I-lim, respectively. Fisher-Sne deckor F-test and Student's t-test statistical data are presented toge ther with corresponding critical values for the three electrochemical parameters obtained in the manual and instrumental polishing modes. Th e reproducibility of all measured data is significantly improved when the electrode is polished after each experiment. The mean values of th e limiting currents were significantly better using the instrumental r ather than the manual polishing method. However, with respect to uncer tainty of the experimental values, instrumental polishing gave the bes t estimates of the measured parameters; confidence intervals were very small for E(1/2) and (E(3/4) - E(1/4)) potential measurements, being +/-0.20 and +/-0.36 mV for E(1/2) values and 0.11 and 0.19 mV for (E(3 /4) - E(1/4)) at 1 and 6 mu m electrodes, respectively. The instrument designed for polishing microelectrodes is also described.