Electrocatalytic Reduction of Nitrite Ion on a Toluidine Blue Sol‐Gel Thin Film Electrode Derived from 3‐Aminopropyl Trimethoxy Silane

An organically modified sol‐gel electrode using 3‐aminopropyltrimethoxy silane for covalent immobilization of a redox mediator namely toluidine blue has been reported. Cyclic voltammetric characterization of the modified electrode in the potential range of 0.2 V to ?0.6 V exhibited stable voltammetric behavior in aqueous supporting electrolyte with a formal potential of ?0.265 V vs. SCE, corresponding to immobilized toluidine blue. The electrocatalytic activity of the modified electrode when tested towards nitrite ion exhibited a favorable response with the electrocatalytic reduction of nitrite occurring at a reduced potential of ?0.34 V. A good linear working range from 2.94×10^?6 M to 2.11×10^?3 M with a detection limit of 1.76×10^?6 M and quantification limit of 5.87×10^?6 M was obtained for nitrite determination. The stable and quick response (4 s) of the modified electrode towards nitrite under hydrodynamic conditions shows the feasibility of using the present sensor in flow systems. Significant improvements in the operational stability by overcoming the leachability problem and repeatability with a relative standard deviation of 1.8% of the TB thin film sensor have been obtained by the strategy of immobilization of the mediator in the sol‐gel matrix.