The Nafion/lead-ruthenium oxide pyrochlore (Pb2Ru1.75Pb0.25O7-y) chemically modified electrode (CME) exhibits an excellent electrocatalytic response towards the amitrole oxidation. It is proposed that the electrochemically active Ru-VI/IV present in the octahedral site of the pyrochlore network mediates the oxidation of amitrole. Rotating disk electrode (RDE) experiments were carried out to evaluate the basic catalytic mechanism on the CME. The occurrence of Michaelis-Menten type kinetics on the CME for the amitrole oxidation reaction was demonstrated and the Michaelis-Menten constant (K-m), electrochemical rate constant (k(e)＇) and the catalytic rate constant (k(c)) were evaluated. The electrocatalytic behavior is further developed as a sensitive detection scheme for amitrole using both square-wave voltammetry and flow-injection analysis. Under optimized conditions, the calibration curve is linear up to 250 mu M with a detection limit of 0.38 mu M (signal/noise = 3) in square-wave voltammetry. For flow-injection analysis, the linear range is 0-100 mu M with a detection limit of 0.15 ng in 20 mu l of sample. (C) 2000 Elsevier Science Ltd. All rights reserved.