DETERMINATION OF VANADIUM BY SOLID-PHASE SPECTROPHOTOMETRY AFTER ITS PRECONCENTRATION AS AN ERIOCHROME-CYANINE-R COMPLEX ON A DEXTRAN-TYPE EXCHANGER

A method is described for the determination by solid phase spectrophot ometry (SPS) of trace amounts of vanadium in natural water and crude p etroleum samples. The procedure is based on fixation on a dextran-type anion exchanger of the complex V(IV)-Eriochrome Cyanine R. The absorb ance of the gel, at 563 and 750 nm, packed in a 1 mm cell, is measured directly. Vanadium can be determined in the 0.6-25.0 mu g l(-1) range with a relative standard deviation of 2.2%. The comparison of the SPS method and the gallic acid persulphate method shows that the linearit y, analytical sensitivity and precision were better for the SPS method , and that the latter method has lower detection and quantification li mits than the gallic acid persulphate method.