As expected, in the absence of H2O2, no significant current was observed. However, increasing the amount of H2O2 showed increased cathodic peak current intensity due to the reduction of H2O2. In order to confirm whether the change in current intensity observed was due to the enzymatic catalytic reduction of H2O2, control experiments in the absence of HRP were carried out. At both the bare electrode (Pt) and polymer modified surface (Pt==PANI) no H2O2 reduction current was observed at 200mV. This is because the reduction reaction of H2O2 at both electrodes in the absence of HRP is very slow and usually occurs at higher potentials. The difference in the observations made for the control experiments (Pt and Pt=PANI) compared to that for Pt=PANI=HRP confirms that the increase in the cathodic current was due to the direct electron transfer between the HRP molecules and the electrode (L. Wang and Wang 2004). Moreover, PANI provides a suitable platform for the immobilization of HRP on the platinum electrode surface and it also mediates in electron transfer between HRP and the electrode (Gerard, Chaubey,