Formation of chromium(IV,V)-ethylenediamine-N,N,N',N'-tetraacetate and its application to spectrophotometric determination of cobalt(II) and chromium(VI).

Abstract
Spectrophotometric and electron spin resonance (ESR) studies on the formation of chromium(IV, V)-ethylene- diamine-N, N, N′, N′-tetraacetate (EDTA) and the spectrophotometric determination of chromium(VI) and cobalt(II) are described. Chromium(V)-EDTA, formed by the oxidation of cobalt(II)-EDTA with chromium(VI) in the presence of excess EDTA and chromium(VI), gives two narrow ESR absorption lines with a g-value of 1.969 and intense absorption at 550nm. The formation of chromium(IV, V)-EDTA depended to a fair degree on the solution pH and the concentration of free excess EDTA. Chromium(IV, V)-EDTA is stable for at least 30min under optimal conditions. The color system obeyed Beer′s law up to 3.8μg/cm3 Co(II) and 3.4μg/cm3 Cr(VI).

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