HR: 0800h
AN: B41B-0201    [Abstracts]
TI: Development electrochemical in-situ pH-pCO2-ORP sensor
AU: * Shitashima, K
EM: shita@criepi.denken.or.jp
AF: Central Research Institute of Electric Power Industry, 1646, Abiko, Abiko, 270-1194 Japan
AU: Koike, Y
EM: ykoike@rite.dcc.co.jp
AF: CERES Inc., 1646, Abiko, Abiko, 270-1166 Japan
AU: Kyo, M
EM: kyom@jamstec.go.jp
AF: JAMSTEC, 3173-25, Showa-machi, Kanazawa-ku, Yokohama, 236-0001 Japan
AU: Henmi, H
EM: hemmi@mebius-at.co.jp
AF: Mebius Advanced Technology, Nishiogi-House 105, 3-31-6, Nishiogikita, Suginami-ku, Tokyo, 164-0042 Japan
AB: The pH and pCO2 of seawater are an important factor that affects the thermodynamic state of all various acid-base systems and biological activity in the ocean. In recent years, in-situ measurement using pH and/or pCO2 sensors has attracted attention in relation to global warming issues. We developed the electrochemical in-situ pH-pCO2-ORP sensors for measurement of these parameters in seawater through the water column in high precision. The pH sensor was used an ion sensitive field effect transistor (ISFET) for the pH electrode and a chlorine ion selective electrode (Cl-ISE) for the reference electrode. Both these electrodes have solid-type construction and therefore have high pressure and shock resistance and can be used satisfactorily in deep-sea conditions. For the pCO2 sensor, the pH sensor was sealed with a gas permeable membrane filled with the inner solution. The pH sensor can detect the pCO2 change as the inner solution pH changes which is caused by penetration of carbon dioxide through the membrane. An amorphous Teflon membrane manufactured by U.S. DuPont (Teflon AF) was used as the gas permeable membrane for this pCO2 sensor. The ORP sensor was used a platinum or gold electrode for the working electrode and Cl-ISE for the reference electrode. The sea tests using those sensors were carried out in various locations of the ocean, high accuracy, quick response, and long-term stability have been achieved. In the field, the response speed of the developed pH sensor is 1 second or less, and the measurement accuracy is _0.005 pH. The in-situ (3000m depth, 1.81/4C) response time of the pCO2 sensor was less than 60 seconds.
DE: 0428 Carbon cycling (4806)
DE: 0450 Hydrothermal systems (1034, 3017, 3616, 4832, 8135, 8424)
DE: 0452 Instruments and techniques
DE: 1050 Marine geochemistry (4835, 4845, 4850)
DE: 4894 Instruments, sensors, and techniques
SC: Biogeosciences [B]
MN: Fall Meeting 2005