Kinetic study and analytical applications of micellar catalyzed reactions of 1-fluoro-2,4-dinitrobenzene with inorganic thioanions using a fluoride-selective electrode

Abstract

A kinetic study and analytical applications of the CPC micellar catalyzed reactions of 1-fluoro-2,4-dinitrobenzene (FDNB) with inorganic thioanions (sulfide, sulfite and thiosulfafte) using a fluoride-selective electrode is described. Reaction orders (unity for both FDNB and thioanion) and experimental stoichiometric reaction-rate constants were calculated from initial slope measurements (Δ E/Δ t) at various pH values (4–9). Calibration graphs for quantitative determinations (4.5–45 μM for sulfide, 2.4–75 μM for thiosulfate and 6.6–75 μM for sulfite) are constructed using the initial rate approach. The proposed method has been applied to the determination of sulfide in spiked seawater samples using the multiple standard addition approach with a mean relative error of 5.5%. The application of this micellar catalyzed reaction in the differential kinetic analysis of binary mixtures of sulfide–thiosulfate and sulfite–thiosulfate, using the proportional equations approach at pH 5.5 and 8.0, was unsuccessful due to the interactions of the two analytes, which can be explained using the ion-exchange/pseudophase model of micellar catalysis. However, the use of multiple linear regression approach on a sufficient number of standard binary mixtures can confront this drawback.