Kinetic studies on the reaction of N-(2-hydroxyethyl)ethylenediamine-N,N′,N′-triacetate chromium(III) with hydrogen peroxide

Abstract

The rate of reaction of Cr(III)L (L=N-(2-hydroxyethyl)ethylenediamine-N,N 0 ,N 0 -triacetate) with hydrogen peroxide was studied in aqueous media and was found to yield Cr(VI) over the temperature range of 25-41°C. The reaction was followed spectrophotometrically at 396 nm under pseudo-first order conditions with hydrogen peroxide in a large excess. The reaction follows first-order kinetics in Cr(III). The dependence of the rate constant on hydrogen peroxide concentration is attributed to the formation of an intermediate between the monohydroxy chromium(III) complex and hydrogen peroxide which decomposes in the rate determining step. At high hydrogen peroxide concentration, the order is changed from first to zero order.The values of the intramolecular electron transfer rate constant, the formation constant of the intermediate complex and the activation parameters were calculated.

Chromium Speciation by HPLC-DAD/ICP-MS: Simultaneous Hyphenation of Analytical Techniques for Studies of Biomolecules

“…NH 4 NO 3 was used to prepare the mobile phase; the aqueous solution was adjusted to pH 7 with NH 4 OH (28% NH 3 in water, ≥99.99% purity, Sigma Aldrich, USA), Table 1 . The monitored wavelengths for [Cr(III)-EDTA] − and Cr(VI) were 550 nm [ 15 , 16 , 17 , 18 , 19 ] and 371 nm [ 15 , 20 ], respectively. The calibration curve for the total determination of Cr was prepared in aqueous medium from the sequential dilution of the standard solution of Cr(VI) at concentrations 1; 5; 10; 50; 100 e 250 µg L −1 ( Table 2 ).…”