Multiparametric Standard Seawater (MSSW) is being developed based on the technology used to manufacture the reference material for nutrients in seawater (RMNS), without adding mercuric chloride to sterilize it, but by adopting aluminum bottles and plastic inner caps with high impermeability to gas and water vapor. The history, current status, and future plans for the development of MSSW for measurements of Practical Salinity, density, dissolved inorganic carbon, total alkalinity, pH, dissolved oxygen (DO), and dissolved organic matter are discussed. Substances that interfere with the Winkler method for DO determination (nitrite, iodate, and hydrogen peroxide) were evaluated for MSSW. The values of the parameters of interest were relatively homogeneous, but the concentrations of dissolved organic carbon depended on the serial number in the lot tested. Long-term stabilities were good in most cases, but DO concentrations began to gradually decrease immediately after production and appeared to stabilize a few years later. The Practical Salinity also tended to decrease (–0.00015 year–1), and the cause of the decreasing trend urgently needs to be clarified. One possibility is an increasing trend (about +0.00015 year–1) of the Practical Salinity of IAPSO standard seawater for salinity measurements.
Uchida H., Murata A., Wakita M., Mitsuda H., Nagasawa Y., Tanaka T., Kayukawa Y., Takeda K., Ito K., Yoshimura T. & Sasano D., 2025. Chapter 12 – Development of multiparametric standard seawater (MSSW) for CO2 parameters, dissolved oxygen, and density of seawater. In: Aoyama M., Cheong C. & Murata A. (Eds.), Chemical Reference Materials for Oceanography: History, Production, and Certification, pp. 203-235. Singapore: Springer Nature Singapore. Chapter.
