A study of the aerobic reaction between dopamine and Fe(III) in the presence of S2O3 2−
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The reaction between Fe(III) and dopamine in aqueous solution in the presence of Na2S2O3 was followed through UV–Vis spectroscopy, pH and oxy-reduction potential (Eh) measurements. The formation and quick disappearing of the complex [Fe(III)HL1−]2+, HL1− = monoprotonated dopamine was observed with or without S2O3 2− at pH 3. An unexpected reaction occurs in presence of thiosulfate forming the stable anion complex [Fe(III)(L2−)2]1−, L2− = dopacatecholate (λ = 580 nm) and the auto-increasing of the pH, from 3 to 7. It was proposed that H+ and molecular oxygen are consumed by free radical thiosulfate formed during the reaction.
KeywordsDopamine Thiosulfate Aerobic Reaction Na2S2O3 Dioxolene
The authors thank the CNPq, Fundação Araucária and FAEPE/UEL for the financial support. Waleria P. Silva is thankful to CNPq for the scholarship.
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