By immersion of enzymic modified electrode in substrate solution, analyte migrates toward the interior of the layer and converses by reaction with the immobilized enzyme [32]. Chronoamperometric measurements consist of applying a fixed potential at the working electrode and monitoring the current resulting, which is directly proportional to the analyte concentration (Fig. 5). Amperometry responses of biosensor to a solution of 1 mM urea inconstant potential (+0.3 V vs. Ag/AgCl) in phosphate buffer 0.1 Mat different pH values were shown in Fig. 6. Optimum response of biosensor was obtained at pH 7.2. Urease can denature and hence reduces enzyme activity in lower or higher of pH 7.2.