Fluorescence properties of thionine and fluorometric determination of sulfide ions as thionine

Abstract

The fluorescence properties of thionine and Methylene Blue were studied. Fluorescence of thionine was proved to be due to a hyperconjugated charged quinoid structure of thiazine ring. The fluorescence quantum yield of thionine is larger than that of Methylene Blue. These findings were applied to the quatitative analysis of sulfide ion. Aqueous sulfide ion reacts p-phenyl-enediamine in the presence of Fe(III) to form fluorescent thionine. The fluorescence of the product is measured sensitively and reliably, and it's concentration is determined in the range of (0.2~10) X 10-7 mol dm-3 in acidic solution (pH 0.5). © 1988, The Japanese Pharmacological Society. All rights reserved.