Development of a sensor for the detection of nitrite using a glassy carbon electrode modified with the electrocatalyst [Os(bipy) 2(PVP) 10Cl]Cl

Abstract

The electrocatalytic polymer [Os(bipy) 2(PVP) 10Cl]Cl, where bipy = 2,2′-bipyridyl and PVP = poly(4-vinylpyridine), was used to modify glassy carbon for use in planar flow cells and conventional electrochemical cells for the reductive electrochemical detection of nitrite. The electrocatalyst accelerates a slow electrochemical reduction of nitrite via a two-step reduction process resulting in a 70-fold increase in response compared with the unmodified electrode. The detector response was evaluated with regard to flow-rate, applied potential, electrolyte pH and surface coverage of the polymer film. A mechanism for the two-step reduction process is proposed. The detector response appears to be limited by the rate constant of the mediated electrochemical reaction. A linear response range extending from 5 × 10 −6 to 1 × 10 −2 M nitrite was obtained, with a detection limit of 0.23 ng ml −1 for the planar flow cell and 0.23 ng ml −1 for a conventional electrochemical cell. The performance of the sensor was assessed with respect to stability, selectivity and interference. The sensor was applied to the determination of nitrite in saliva.