Abstract: A potentiometric electrochemical analysis method, which comprises placing by capillary action an aqueous sample liquid to be tested for the presence of a quantity of an analyte in the sample liquid, in each of two compartments of an electrochemical analysis cell, wherein the aqueous sample liquid so placed in each compartment is in electrochemical contact with one of two electrodes forming part of the cell, wherein the electrodes are insensitive to the analyte, and wherein the compartments are separated by an electroactive barrier which is sensitive to or selective for the analyte, the barrier not being in electrical contact with either electrode except through the medium of the sample liquid, the method further comprising changing the amount of the analyte material in a selected one of the compartments by adding thereto a predefined standard quantity of analyte, measuring the resulting cell potential and determining the concentration of the analyte in the sample liquid, the predefined standard quantity of an

Abstract: An electrochemical cell comprising two electrodes, wherein one of said electrodes is suitable for use as a reference electrode in electrochemical measurements, said device comprising (a) a capillary fill cell capable of receiving a small volume of aqueous sample liquid, said cell incorporating (b) a redox electrode located within said capillary fill cell, and (c) a reagent layer comprising quinhydrone located in said cell in a dry adherent water-soluble layer adherent to an inner surface of said cell opposite to or overlying said redox electrode and capable of dissolving during use in aqueous sample liquid in the region of said redox electrode.