ELECTROCHEMICAL SENSOR FOR PH MEASUREMENT

摘要

A method of determining the pH of an aqueous liquid which contains little or no buffer, such as does not contain more than 0.01 moles per litre of pH-buffering partially dissociated acid, base and/or salt, uses an electrode with at least one redox active compound immobilized thereon convertible electrochemically between reduced and oxidized forms with transfer of at least one proton between the compound and the aqueous liquid. Varying potential is applied to the electrode, observing current flow as potential is varied, determining the applied potential at a maximum current for redox reaction of the compound, and determining pH from the potential at maximum current. The electrode has a covering layer which separates the redox active compound from the aqueous liquid but selectively allows the passage of hydrogen ions between the redox active compound and the aqueous liquid. The presence of the covering layer enhances accuracy of the measurement of pH of the aqueous liquid.

主权项

1. A method of determining the pH of an aqueous liquid, comprising
contacting the liquid with an electrode comprising a substrate with at least one redox active compound immobilized thereon, the redox active compound comprising at least one functional group convertible electrochemically between reduced and oxidized forms with transfer of at least one proton between the compound and the aqueous liquid, applying potential to the electrode, observing current flow and determining pH from observed data, wherein the electrode has a covering layer which separates the redox active compound from the aqueous liquid but allows the passage of hydrogen ions between the redox active compound and the aqueous liquid, and wherein the concentration of buffer in the aqueous liquid is sufficiently low that the presence of the covering layer enhances accuracy of the measurement of pH of the aqueous liquid.