Analytical Sciences

Oxygen Indicator Composed of an Organic/Inorganic Hybrid Compound of Methylene Blue, Reductant, Surfactant and Saponite

Makoto SUMITANI,*^,*** Shinsuke TAKAGI,*^,** Yoshihiko TANAMURA,*^,** and Haruo INOUE*^,**

*Department of Applied Chemistry, Graduate Course of Engineering, Tokyo Metropolitan University, 1-1 Minami-ohsawa, Hachiohji, Tokyo 192-0397, Japan
**CREST, Japan Science and Technology Agency, 4-1-8, Honcho, Kawaguchi, Saitama 332-0012, Japan
***Tokyo Research Laboratory, Mitsubishi Gas Chemical Company, Inc., 1-1 Niijuku 6-chome, Katsushika, Tokyo 125-0051, Japan

An organic/inorganic hybrid compound consisting of methylene blue, a cationic surfactant and a reductant intercalated into saponite was found to serve as an oxygen indicator that changes color in the presence of oxygen. A mixture of a blue colored dye, methylene blue, a reductant in the form of ascorbic acid or reducing sugar, and cetyltrimethylammonium ion intercalated into synthetic saponite became colorless in an atmosphere having an oxygen concentration of less than 0.1 vol%, and then returned to its blue color as a result of subsequent exposure to air. An oxygen indicator, in the form of a thin film coated on paper prepared by adding a pigment, phloxine B, to the above organic/inorganic hybrid compound, exhibited a pink color at oxygen concentrations of less than 0.1 vol%, and a blue color at oxygen concentrations of higher than 0.5 vol%. In addition, this oxygen indicator exhibited superior photo-fading resistance and storage stability compared with indicators using only methylene blue as the functional dye.

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