Patent ID: 8758593

Claim:
A working electrode for an electrochemical sensor for measuring pH of a fluid, comprising: a conducting substrate; a first set of redox species coupled with the conducting substrate, wherein the first set of redox species comprises one or more non-polymeric redox species that are sensitive to pH, and wherein the coupling of the first set of redox species with the conducting substrate comprises one of the first set of redox species being chemically coupled with the conducting substrate, the first set of redox species being coated on the conducting substrate and the first set of redox species being deposited on the conducting substrate; and a polymer layer which consists of polymer and which directly covers at least an area of the conducting substrate where the conducting substrate is coupled with the first set of redox species so that the polymer layer directly covers the first set of redox species, the polymer layer being configured to allow hydrogen ions to diffuse through the polymer layer to interact with the first set of redox species and to prevent diffusion of the non-polymeric redox species from the working electrode.