Development of In-situ pH Sensor Using ISFET

A0115 Kiminori Shitashima Environmental Science Department, Central Research Institute of Electric Power Industry (CRIEPI)

A0116 Masanori Kyo Marine Technology Department, Japan Marine Science and Technology Center (JAMSTEC)

A0117 Yuichi Koike Research Institute of Innovative Technology for the Earth (RITE)

A0118 Hideaki Henmi Mebius Advanced Technology

The development of in-situ chemical sensor plays a key role in

understanding of chemical and biological processes in the ocean. In

deep-sea hydrothermal systems, in-situ mapping and long term

monitoring of the chemical parameters in hydrothermal plumes are the

most efficient methods for trying to understand hydrothermal discharge.

In-situ chemical sensors are necessary for these purposes.

Hydrothermal plumes show pH anomalies because carbon dioxide and/or

hydrogen sulfide-rich fluids are mixed into the ambient sea water. We

developed an in-situ pH sensor for mapping and long term monitoring of

pH anomalies at hydrothermally active areas. The in-situ pH sensor

employs an ion sensitive field effect transistor (ISFET) as a pH

electrode, and the Cl-ion selective electrode (Cl-ISE) as a reference

electrode. The ISFET is a semiconductor that can measure ion

concentration in aqueous phase and has a quick response (within a

nanosecond), high accuracy (0.01~0.005pH)and pressure-resistant.