ELECTROCHEMICAL SENSOR OF NITRITE BASED ON AN INORGANIC FILM-MODIFIED GLASSY-CARBON ELECTRODE

The electrocatalysis of nitrite in solutions at an inorganic film modified glassy carbon electrode was studied. The modifier was an electrodeposited thin inorganic film of the copper-heptacyanonitrosylferrate (CuHNF). Cyclic voltammetry of the modified electrode in a nitrite solution revealed that both oxidation and reduction of nitrite were catalyzed and the electrocatalytic currents were controlled by the diffusion of nitrite. Voltammetric and amperometric responses were investigated. When applied as an amperometric sensor in a flow injection system, the modified electrode permitted detection at -0.55 V, over 500 mV lower than at the naked electrode surface. A linear response range extending from 1 x 10(-6) to 1 x 10(-3) M nitrite was obtained, with a detection limit of 3 x 10(-7) M. The relative standard deviation for 50 repetitive injections with a 5 x 10(-5) M nitrite solution was less than 4%. The procedure was applied to the determination of nitrite in saliva and nitrate.