Extraction and simultaneous spectrophotometric determination of vanadium(IV) and vanadium(V) in admixture with 2-hydroxyacetophenone oxime

Abstract

Vanadium(IV) and vanadium(V) in the presence of 2-hydroxyacetophenone oxime were extracted quantitatively into chloroform in the pH ranges 3.6–4.5 and 2.7–4.1, respectively. The organic layer showed absorbance maxima at 345 and 350 nm for V^IV and V^V, respectively. Studies of the behaviour of V^IV were also carried out at a wavelength of 350 nm. Vanadium(V) absorbed considerably beyond 380 nm whereas V^IV had negligible absorbance in this region. The absorbance of the organic layer, for both V^IV and V^V, was unaltered, even after 4 d. The composition of the complexes formed was established to be 1 : 2 (metal : ligand) by Job's method. Interference studies were carried out for both V^IV and V^V and methods are suggested for eliminating interference by foreign ions. Both V^IV and V^V are extracted quantitatively at pH 4; this extraction was exploited successfully for the simultaneous determination of V^IV in the range 1–3 µg ml^–1 and V^V in the range 1–6 µg ml^–1 by measuring the absorbances at 350 and 400 nm, respectively.