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 plant by reduction with ascorbic acid in sulphuric acid medium. An intermediate V(IV)–V(V) species formed during the reduction reaction allowed the determination of V(V) from 0.5 to 60 g 1 −1 A novel concept is also presented in which vanadium in the 5 + oxidation state is used to determine vanadium in the 4 + oxidation state, by formation of a mixed 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 to 1 g 1−1 in aqueous scrubbing solutions was determined using a reagent stream containing 1 g 1−1 V(V).