Spectrophotometric determination of vanadium(V) with N-phenylcinnamohydroxamic acid

N-Phenylcinnamohydroxamic acid (PCHA) reacts with vanadium(V) to form a 1:2 (V:PCHA) bluish-violet coloured complex, quantitatively extractable into chloroform from 3-9 M hydrochloric acid solutions. The spectrum of the complex in the visible region exhibited a broad absorption maximum at 545 nm with a molar absorptivity of 6300 M(-1) cm(-1). The coloured system obeyed Beer's law in the concentration range of 0.5-10 mu g ml(-1) of vanadium. The effects of several experimental variables on the extraction of the complex have been studied to establish the optimum conditions for the determination of vanadium(V). On the basis of these studies a simple, precise, and sensitive method has been developed for the spectrophotometric determination of vanadium(V). The method has been successfully applied to the determination of vanadium in standard steels.