This paper demonstrates a new and simple approach based on a continuous pulsed-potential (CPP) method for the preparation of reproducible nanostructure and nanoporous thin film on the polycrystalline gold electrodes. The fabrication process involves pulsed electrochemical oxidation and reduction of gold electrode in the sulfuric acid solution without using additional reagents. Effect of various parameters including pulse height, pulse time, pulse number and relaxation time on the enhancing of hexacyanoferrate (HCF) redox behaviour, as a probe, were investigated and optimized. Electrochemical, scanning electron microscopy (SEM) and atomic force microscopy (AFM) studies show the formation of a nanoporous thin film and sharp nanostructure edges on the gold electrode that considerably enhances electrocatalysis of HCF and provides useful conditions for the electroanalysis by the modified electrode. In addition, the electrocatalytic behaviour of this modified electrode was exploited as a sensitive detection system for the determination of metronidazole in pharmaceutical and human urine samples, by using cyclic voltammetry (CV) and hydrodynamic methods. Under optimized conditions, this method shows linear dynamic ranges of 0.5-10.0 and 20.0-800.0 mu M with the calculated detection limit (S/N = 3) of 0.15 mu M and a precision of <5%. (C) 2009 Elsevier Ltd. All rights reserved.