The negatively charged polymer polyester sulfonic acid (Eastman-AQ, abbreviated to AQ), positively charged polymer polyvinyl pyridine (PVP) and mediator Os(bpy)(3)(2+) were used to construct composite modified glassy carbon (GC) electrodes (abbreviated to GC/AQ-Os(bpy)(3)(2+)-PVP). The reduction of NO2- in acidic solution was taken as a model reaction to explore the properties of the modified electrode. On the steady state polarization curve of NO2- reduction there were two well-developed waves with much enhanced plateau current densities and positively shifted half-wave potentials compared with bare GC electrodes. In 0.05 mol/l 2 and half-wave potential H2SO4 + 5 mmol/l NO2- the modified electrode exhibited plateau current densities of 723 and 1153 muA cm(-2) shifts of 0.29 and 0.56 V for the first and second current wave, respectively, showing promising potential for nitrite detection. The catalytic activity for NO2- reduction did not decrease appreciably over 4 months. A number of relevant kinetic and thermodynamic parameters are estimated experimentally. NO2- reduction at the composite modified electrodes is suggested to follow the SR mechanism (pure kinetic conditions involving mutual compensation between a catalytic reaction and substrate diffusion in the film in addition to diffusion in the solution phase) according to the Saveant-Andrieux theory. (C) 2003 Elsevier B.V. All rights reserved.