Development of an automated transportable continuous system to measure the total alkalinity of seawater

Shoji Yamamoto; Hajime Kayanne; Nori Fujita; Yukari Sato; Haruko Kurihara; Saki Harii; Akihide Hemmi; Andrew G Dickson

doi:10.1016/j.talanta.2020.121666

Development of an automated transportable continuous system to measure the total alkalinity of seawater

Talanta. 2021 Jan 1:221:121666. doi: 10.1016/j.talanta.2020.121666. Epub 2020 Sep 15.

Authors

Shoji Yamamoto¹, Hajime Kayanne², Nori Fujita³, Yukari Sato⁴, Haruko Kurihara⁵, Saki Harii⁶, Akihide Hemmi⁷, Andrew G Dickson⁸

Affiliations

¹ National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8563, Japan. Electronic address: shoji-yamamoto@aist.go.jp.
² Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan. Electronic address: kayanne@eps.s.u-tokyo.ac.jp.
³ Department of Earth and Planetary Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan.
⁴ National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8563, Japan.
⁵ Department of Chemistry, Biology, and Marine Science, University of the Ryukyus, Senbaru 1, Nishihara, Okinawa, 903-0213, Japan.
⁶ Tropical Biosphere Research Center, University of the Ryukyus, 3422 Sesoko, Motobu, Okinawa, 905-0227, Japan.
⁷ Mebius Advanced Technology Ltd., 3-31-6 Nishiogi-kita, Suginami-ku, Tokyo, 167-0042, Japan.
⁸ Scripps Institution of Oceanography (MC0244), University of California San Diego, 9500 Gilman Drive, La Jolla, CA, 92093-0244, USA.

PMID: 33076173
DOI: 10.1016/j.talanta.2020.121666

Abstract

Anthropogenic CO₂ emissions are contributing to global warming and ocean acidification. Rapid and accurate measurements of seawater carbonate chemistry are critical to understand current changes in the ocean and to predict future effects of such changes on marine organisms and ecosystems. Total alkalinity (A_T) measurements can be used to directly determine the calcification rate, but they are time-consuming and require large sample volumes. Herein, we describe an automated and transportable flow-through system that can conduct continuous A_T measurement using an ion sensitive field effect transistor (ISFET) - Ag/AgCl sensor and three different reference materials. The response time, stability, and uncertainty of our system were evaluated by comparing A_T values of calibrated reference materials to those calculated by our system. Our system requires only small amounts of seawater (<10 mL) and a short time per sample (<5 min) to produce results with a relative uncertainty of less than 0.1% (approx. 2.2 μmol kg^-1). This system is expected to facilitate easy and rapid in-situ measurement of A_T. Continuous A_T measurements would enable us to determine short-term calcification responses to changes in light or temperature and improve our understanding of the metabolic mechanisms of creatures such as corals.

Keywords: Continuous measurement; ISFET; Seawater; Titration; Total alkalinity; Transportable.