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Sensors 2015, 15(4), 7898-7912; doi:10.3390/s150407898

A Simple Method for Decreasing the Liquid Junction Potential in a Flow-through-Type Differential pH Sensor Probe Consisting of pH-FETs by Exerting Spatiotemporal Control of the Liquid Junction

1
Department of Mechanical Engineering, Faculty of Engineering, Aichi Institute of Technology, 1247 Yachigusa, Yakusa Cho, Toyota City, Aichi Prefecture 470-0392, Japan
2
Cardiovascular Physiology, Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama University, 2-5-1 Shikata-cho, Kita-ku, Okayama Prefecture 700-8558, Japan
3
First Department of Physiology, Kawasaki Medical School, 577 Matsushima, Kurashiki-City, Okayama Prefecture 701-0192, Japan
*
Author to whom correspondence should be addressed.
Academic Editor: W. Rudolf Seitz
Received: 5 January 2015 / Revised: 24 March 2015 / Accepted: 25 March 2015 / Published: 1 April 2015
(This article belongs to the Section Chemical Sensors)
View Full-Text   |   Download PDF [884 KB, uploaded 1 April 2015]   |  

Abstract

The liquid junction potential (LJP), the phenomenon that occurs when two electrolyte solutions of different composition come into contact, prevents accurate measurements in potentiometry. The effect of the LJP is usually remarkable in measurements of diluted solutions with low buffering capacities or low ion concentrations. Our group has constructed a simple method to eliminate the LJP by exerting spatiotemporal control of a liquid junction (LJ) formed between two solutions, a sample solution and a baseline solution (BLS), in a flow-through-type differential pH sensor probe. The method was contrived based on microfluidics. The sensor probe is a differential measurement system composed of two ion-sensitive field-effect transistors (ISFETs) and one Ag/AgCl electrode. With our new method, the border region of the sample solution and BLS is vibrated in order to mix solutions and suppress the overshoot after the sample solution is suctioned into the sensor probe. Compared to the conventional method without vibration, our method shortened the settling time from over two min to 15 s and reduced the measurement error by 86% to within 0.060 pH. This new method will be useful for improving the response characteristics and decreasing the measurement error of many apparatuses that use LJs. View Full-Text
Keywords: pH; ISFET; pH-FET; differential pH sensor probe; liquid junction potential pH; ISFET; pH-FET; differential pH sensor probe; liquid junction potential
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Yamada, A.; Mohri, S.; Nakamura, M.; Naruse, K. A Simple Method for Decreasing the Liquid Junction Potential in a Flow-through-Type Differential pH Sensor Probe Consisting of pH-FETs by Exerting Spatiotemporal Control of the Liquid Junction. Sensors 2015, 15, 7898-7912.

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