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APPLICATION OF CYCLOVOLTAMMETRIC MEASUREMENT OF pH VALUE USING METAL-METAL OXIDE-BASED SENSORS

IP.com Disclosure Number: IPCOM000061565D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 3 page(s) / 28K

Publishing Venue

IBM

Related People

Andreshak, JC: AUTHOR [+3]

Abstract

A metal-metal oxide electrode can be used to measure the pH of a solution by utilizing cyclovoltammetry. Cyclovoltammetry allows the chemical reaction preceding the oxidation or reduction voltage shift reaction to be controlled so that the integrity of the oxide layer on the electrode surface is preserved for accurate measurement. Cyclovotammetry is an electroanalytical technique in which a voltage is applied at a predetermined scan rate and the current-voltage relationship is then examined. However, the voltage shifts due to oxidation or reduction peaks are affected by the integrity of the electrode surface since these peak shifts represent a surface reaction. The integrity of the electrode surface has been found to depend on the electrochemical reaction prior to the voltage shift reaction.

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APPLICATION OF CYCLOVOLTAMMETRIC MEASUREMENT OF pH VALUE USING METAL-METAL OXIDE-BASED SENSORS

A metal-metal oxide electrode can be used to measure the pH of a solution by utilizing cyclovoltammetry. Cyclovoltammetry allows the chemical reaction preceding the oxidation or reduction voltage shift reaction to be controlled so that the integrity of the oxide layer on the electrode surface is preserved for accurate measurement. Cyclovotammetry is an electroanalytical technique in which a voltage is applied at a predetermined scan rate and the current-voltage relationship is then examined. However, the voltage shifts due to oxidation or reduction peaks are affected by the integrity of the electrode surface since these peak shifts represent a surface reaction. The integrity of the electrode surface has been found to depend on the electrochemical reaction prior to the voltage shift reaction. Control of these preceding shift reactions provides a clean oxide layer on the surface of the metal-metal oxide electrode. In addition, it has also been found that any other unwanted reactions, which take place after the voltage shift and which are detrimental to the electrode surface, can be eliminated by using cyclovoltammetry. In the figure, two cyclovoltammograms for different pH solutions are shown. Peaks A and A' represent the voltages at which the preceding reactions occur, while peaks B and B' represent the voltage shift reactions. Peaks C and C' represent the voltages at which an unwanted reaction after the voltage shift reaction occurs. As the figure shows, because of the effect on the reactions of B and B' by reactions A and A', respectively, it is desirable to promote reactions A and A' to reach their peaks, and then stop the reaction from proceeding further. The polarity of the voltage scan can then be reversed to detect the voltage peaks B and B'. The above result is achieved by the following process. First, the value of di/dv (in fact, di/dt, for constant voltage-scan rate) is measured simultaneously with the voltage-scan rate. When di/dv = 0, i.e., the voltages at which A and A' are reached, one can ei...