The electrochem. behavior of toluidine blue (TB) at a carbon fiber microdisk electrode was studied. The effect of pH on the electrode process was investigated, and the no. of H+ in the electrode process is 3 at the range of 1.5 ~ 3.7, 2 at pH 3.7 ~ 5.5 or 1 and pH5.5 ~ 10.7, resp. The apparent standard heterogeneous electron transfer rate constant k0', and E0' of TB at various pH on the carbon fiber microdisk electrode were determine The overall electrode reaction mechanism of toluidine blue was proposed. The adsorbability of TB on the electrode was studied, and the kinetics parameters in the control of adsorption process were determine

Key words: ADSORPTION, DIFFUSION COEFFICIENTS, CARBON FIBERS, MICROELECTRODE, ELECTRODE REACTION, PH VALUE