Characterization of an Ion Sensitive Field Effect Transistor and Chloride Ion Selective Electrodes for pH Measurements in Seawater

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• 作者：Yuichiro Takeshita ; Todd R. Martz ; Kenneth S. Johnson ; Andrew G. Dickson
• 刊名：Analytical Chemistry
• 出版年：2014
• 出版时间：November 18, 2014
• 年：2014
• 卷：86
• 期：22
• 页码：11189-11195
• 全文大小：303K
• ISSN：1520-6882

文摘

Characterization of several potentiometric cells without a liquid junction has been carried out in universal buffer, aqueous HCl, and artificial seawater media. The electrodes studied include Ion Sensitive Field Effect Transistor (ISFET) pH electrodes, and Chloride-Ion Selective Electrodes (Cl-ISE) directly exposed to the solution. These electrodes were compared directly to the conventional hydrogen electrode and silver鈥搒ilver chloride electrode in order to report the degree to which they obey ideal Nernstian laws. These data provide a foundation for operating the ISFET|Cl-ISE pair in seawater as a pH sensor. In order to obtain the highest quality pH measurements from this sensor, its response to changes in pH and salinity must be properly characterized. Our results indicate near-ideal Nernstian response for both electrodes over a wide range of pH (2鈥?2) and Cl^{鈥?/sup> molality (0.01鈥?). We conclude that the error due to sub-Nernstian response of the cell ISFET|seawater|Cl-ISE over the range of seawater pH and salinity is negligible (<0.0001 pH). The cross sensitivity of the Cl-ISE to Br鈥?/sup> does not seem to be a significant source of error (<0.003 pH) in seawater media in the salinity range 20鈥?5.}