A voltammetric study was then carried out to examine the effects of pretreatment on the functional characteristics of the microelectrode. The effect of pretreatment on both the faradaic and charging currents are shown in Figs. 2 and 3 respectively. The increase in charging current obtained after pretreatment could be interpreted as being due to an increase in the surface area of the microelectrode. Bjelica et al. [22] have reported that glassy carbon electrodes subjected to prolonged electrolysis at extreme positive potentials caused roughening of the surface. However, the enhanced faradaic current obtained after pretreatment for folic acid would not, alone, be explained by the relatively small increase in surface area indicated by the charging current.