Analytical Sciences

Effect of Ethanol Addition on the Determination of Thiosulfate Based on Reduction of Ce(IV) and Fluorescence Detection of Ce(III)

Ikko MIKAMI, Eri SHIBAYAMA, Manami YUZAWA, and Yasuyuki MIURA

Department of Chemistry, School of Science, Tokai University, 4-1-1 Kitakaname, Hiratsuka 259-1292, Japan

The effect of ethanol addition on the determination of thiosulfate based on the reduction of Ce(IV) and fluorescence detection of Ce(III) was investigated by flow-injection analysis. It was found that the sensitivity of thiosulfate detection was significantly increased by injecting thiosulfate into a mixed solution of Ce(IV) and ethanol, rather than a solution of Ce(IV) alone. This is probably due to trace amounts of thiosulfate accelerating the rate of reduction of Ce(IV) by ethanol: Ce(IV) is slowly reduced by ethanol in the absence of thiosulfate, and thiosulfate serves as a catalyst to the reduction. The detection limits as S/N = 3 for thiosulfate were very low (10⁻⁹ M level).

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