DETERMINATION OF VANADIUM(IV) AND VANADIUM(V) BY FORMATION OF A TRANSIENT MIXED-VALENCE COMPLEX IN A FLOW-INJECTION MANIFOLD

A mixed V(IV)-V(V) species was used for the determination of both V(IV ) and V(V). V(V) was determined in samples from a solvent extraction p lant by reduction with ascorbic acid in sulphuric acid medium. An inte rmediate V(IV)-V(V) species formed during the reduction reaction allow ed the determination of V(V) from 0.5 to 60 g l(-1) A novel concept is also presented in which vanadium in the 5 + oxidation state is used t o determine vanadium in the 4 + oxidation state, by formation of a mix ed valence complex. This complex was shown to be identical to the one formed by reduction of V(V) by ascorbic acid. V(IV) in the range 0.1 t o 1 g l(-1) in aqueous scrubbing solutions was determined using a reag ent stream containing 1 g l(-1) V(V).