Electrochemical sensor

An electrochemical sensor for determining the presence or quantity of an oxidant of interest in an aqueous solution comprising:

• an elongate substrate layer having a first end opposite to a second end;
• first, second and third conductive tracks deposited axially onto the substrate layer in a parallel mutually spaced apart relationship, wherein the first conductive track constitutes a reference electrode, wherein on the second conductive track near to the second end of the substrate layer is a carbon deposit whereby to constitute a counter electrode and on the third conductive track near to the second end of the substrate layer is a carbon deposit whereby to constitute a working electrode, wherein each of the first, second and third conductive tracks terminates near to the first end of the substrate layer in an electrical contact;
• a non-conductive layer deposited on the first, second and third conductive tracks, wherein the non-conductive layer is fabricated to fully expose each electrical contact near to the first end of the substrate layer, to fully expose the carbon deposit on the second conductive track near to the second end of the substrate layer, to fully expose the first conductive track near to the second end of the substrate layer and to partially expose discrete working regions of the carbon deposit of the third conductive track through an array of apertures;
• a reagent formulation deposited on or near to the surface of the working electrode, wherein the reagent formulation includes a reductant;
• and
• a deposit of a supporting electrolyte deposited on the non-conductive layer, wherein the deposit of a supporting electrolyte is deposited on a region of the non-conductive layer between the fully exposed carbon deposit on the second conductive track and the fully exposed first conductive track.