Spectrophotometric determination of vanadium in complex materials using N-m-TMBHA and thiocyanate

Vanadium(V) reacts with N-m-Tolyl-p-methoxy benzohydroxamic acid to form 1:2 (metal to ligand) complex containing a basic V = O group and an acidic V-OH group, which forms addition compounds with thiocyanate to give a hyper and bathochromic effect in chloroform. On the basis of this bathochromic effect of thiocyanate a rapid, selective and sensitive method for the spectrophotometric determination of vanadium(V) has been developed. The blue coloured complex of vanadium(V) is extractable in chloroform having absorption maxima at 580 nm and max 7100 +/- 50 1 X mole-1 cm-1. The method is free from interferences of Mo(VI), W(VI), Zr(IV) and has been successfully applied for the analysis of steels and other complex materials.