Analytical Sciences

Achieving High Time-Resolution with a New Flow-through Type Analyzer for Total Inorganic Carbon in Seawater

Hideshi KIMOTO,*¹  Ken NOZAKI,*² Setsuko KUDO,*³ Ken KATO,*² Akira NEGISHI,*² and Hajime KAYANNE*^3,*⁴

*1 Kimoto Electric Co., Ltd., Funahashi, Tennoji, Osaka 543-0024, Japan
*2 Energy Electronics Institute, National Institutes of Advanced Industrial Science and Technology, AIST Tsukuba Central 2, Umezono, Tsukuba 305-8568, Japan
*3 Japan Science and Technology Corporation, Department of Earth and Planetary Science, The University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan
*4 Department of Earth and Planetary Science, The University of Tokyo, Hongo, Bunkyo, Tokyo 113-0033, Japan

A fully automated, continuous-flow-through type analyzer was developed to observe rapid changes in the concentration of total inorganic carbon (C_T) in coastal zones. Seawater and an H₃PO₄ solution were fed into the analyzer's mixing coil by two high-precision valveless piston pumps. The CO₂ was stripped from the seawater and moved into a carrier gas, using a newly developed continuous-flow-through CO₂ extractor. A mass flow controller was used to assure a precise flow rate of the carrier gas. The CO₂ concentration was then determined with a nondispersive infrared gas analyzer. This analyzer achieved a time-resolution of as good as 1 min. In field experiments on a shallow reef flat of Shiraho (Ishigaki Island, Southwest Japan), the analyzer detected short-term, yet extreme, variations in C_T which manual sampling missed. Analytical values obtained by the analyzer on the boat were compared with those determined by potentiometric titration with a closed cell in a laboratory: C_T(flow-through) = 0.980·C_T(titration) + 38.8 with r² = 0.995 (n = 34; September 1998).

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