A selective spectrophotometric determination of vanadium(V) with 2', 4' -dihydroxyacetophenone benzoylhydrazone

Abstract

2' ,4' -Dihydroxyacetophenone benzoylhydrazone (DHABH) forms a yellow 1:1 complex with V(V) ion in aqueous medium at 0.1-0.6 <i>M </i> CH₃COOH and 40-55°C. The complex which is extracted into 1,2-dichloroethane quantitatively has λ_max at 373 nm. The molar absorptivity, Sandell's sensitivity and standard deviation are caIculated to be 1.25 x 10⁴ lmol^-1 cm^-1, 0.004 µg V cm^-2 and ± 0:005 at 2.0 µg ml ^-1 respectively at 373 nm. Beer's law is valid over the concentration range of 0-7.2 µg V ml^-¹ with an optimum range for accurate determination of 0.8-5.25 ppm of V(V). The colour reaction is free from interferences from as many as 36 cations and 15 anions/complexing agents. The method has been satisfactorily applied for the determination of vanadium in a wide variety of synthetic and natural samples.