Electrochemical pH measurement

摘要

A method of measuring pH of aqueous liquid with little or no buffer present uses an electrochemical pH sensor which comprises a plurality of electrodes with a redox active organic compound attached to an electrode and having at least one functional group convertible electrochemically between reduced and oxidized forms with transfer of at least one proton between the compound and surrounding aqueous phase, wherein the compound has at least one substituent group which promotes hydrogen bonding at a said functional group and thereby increases the reaction rate of proton transfer. The substituent group may form an internal hydrogen bond with a redox-convertible group or may enhance polarity to promote electrostatic interaction with water molecules and reduce activation energy. Such an electrochemical sensor may be used for pH measurement in computer controlled equipment for processing an aqueous liquid.

主权项

1. A method of measuring the pH of an aqueous liquid, comprising
exposing the aqueous liquid comprising buffer at a concentration of 0.01 molar or less to an electrochemical sensor comprising an electrode with a redox active compound immobilized to the electrode with at least one functional group convertible electrochemically between reduced and oxidized forms upon transfer of at least one proton between the compound and surrounding aqueous phase, wherein the reduced form of the redox active compound incorporates a partial structure, wherein the oxidized form of the redox active compound incorporates a partial structure, where the carbon atoms are joined by conjugated bonds in both the reduced form and the oxidized form of the redox active compound, wherein the compound has at least one keto group, which is positioned to participate in internal hydrogen bonding with the at least one functional group in its reduced form and increases the reaction rate of proton transfer by reducing the activation energy for transfer of a proton and/or promoting hydrogen bonding at a said functional group, and observing the redox reaction at the electrochemical sensor.