An improved approach of pH electrode preparation for application in the deep-sea environment

PAN Yi-wen; YE Ying; HAN Chen-hua

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PAN Yi-wen, YE Ying, HAN Chen-hua. An improved approach of pH electrode preparation for application in the deep-sea environment[J]. Haiyang Xuebao, 2010, 32(2): 73-79.

Citation:

PAN Yi-wen, YE Ying, HAN Chen-hua. An improved approach of pH electrode preparation for application in the deep-sea environment[J]. Haiyang Xuebao, 2010, 32(2): 73-79.

PAN Yi-wen, YE Ying, HAN Chen-hua. An improved approach of pH electrode preparation for application in the deep-sea environment[J]. Haiyang Xuebao, 2010, 32(2): 73-79.

Citation:

PAN Yi-wen, YE Ying, HAN Chen-hua. An improved approach of pH electrode preparation for application in the deep-sea environment[J]. Haiyang Xuebao, 2010, 32(2): 73-79.

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An improved approach of pH electrode preparation for application in the deep-sea environment

Department of Ocean science and Engineering, Zhejiang University, Hangzhou 310028,China

Received Date: 2009-06-11
Rev Recd Date: 2009-12-24

Abstract

Abstract

pH is a fundamental parameter in understanding the chemical processes in deep-sea hydrothermal and diffuse flow areas. pH is also considered to be one of the important characteristics that influences the animal distribution within hydrothermal vent sites while pH is also affected by the metabolic processes of the organism. Hence, a accurate access for deep-sea in-situ pH is a common concern of both marine chemists and marine biologists. In the former application of sea trials, two phenomena have been found: one is that the electrode can respond to the chemical abnormality, the other is due to the drifting problem of the electrode. Data acquired by the electrode can only be used as a qualitative evidence for deep-sea research.Two novel approaches to the preparation of iridium oxide electrode are proposed based on the mechanics of molten alkali metal carbonate. Experiments and SEM surface analysis were carried out to characterize the different types of IrO_x electrodes. Including the electrodes prepared by the traditional approach, the results show that all three of them exhibit Nernst response. Comparing both the sensing characteristics and the SEM surface analysis of the three types of IrO_x electrodes, however, the IrO_x electrodes of advanced carbonate-melted methods exhibited better pH sensitivity and stability, and more solid surface. Therefore, it can be speculated that the oxygen contents during the preparation procedure is a key factor that affects the IrO_x film characteristics. Among the three types of IrO_x electrodes, the one prepared by molten mixed carbonate lithium and sodium peroxide showed the best sensing characteristics. It exhibited good reproducibility and sensitivity, small OCP (open circuit potential) drift (＜5 mV) of 7 d continuous pH measurements, long lifetime and remarkable agreement with respect to potential/pH slopes and apparent standard electrode potentials of individual electrodes prepared from the same batch. Although the aging effects caused the apparent standard electrode potential drop about 50 mV after 3 months, the problem could be eliminated by calibration. Therefore, the good performance of the IrO_x electrode prepared by molten mixed carbonate lithium and sodium peroxide may allow this type of IrO_x electrode be suitable for being applied to in-situ deep-sea measurement.
- deep-sea chemical measurement,
- IrO_x electrode,
- pH sensor,
- Nernst response,
- electrode stability

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References(21)

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