Electrode Potentials of a Silver-Silver Chloride Electrode vs. Temperature for Biosensors

Abstract

The aim of this study is to make clear the effect of temperature on the potentials of silver-silver chloride(Ag-AgCl) electrodes in potassium chloride(KCl) and sodium chloride(NaCl) solutions for micro biosensor applications. Non-isothermal coefficients, or thermal coefficient of Ag-AgCl electrodes in the concentrations of 0.1 to 1.0[mol/kg] were experimentally measured in the range of 15 to 45[°C]. The electrode was prepared by electrolytical process in KCl or NaCl solutions. The length and diameter of the electrode are 20[mm] and 3[mm], respectively. The coefficients in KCl solutions were 0.42[mV/°C] in 0.1[mol/kg] and 0.26[mV/°C] in 1.0[mol/kg] and almost the same in NaCl solutions. Isothermal coefficients were also measured. Although the coefficients must theoretically be zero by definition for all temperatures, the difference of potentials between a pair of electrodes which is called as offset voltage appears practically. They were 3∼4[μV/°C] in 0.1[mol/kg] and 0.3[μV/°C] in 1[mol/kg] at the steady state of temperature. The values were depending on the degree of the uniformity of electrode surface.