Spectrophotometric determination of vanadium in fuel oil and stack gas using 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid

Abstract

Vanadium(V) reacts with 2-[2-(3,5-dibromopyridyl)azo]-5-dimethylaminobenzoic acid in aqueous acetone solution to give a blue colour with an absorbance peak at 640 nm. The colour in aqueous acetone solution was stable and the system conformed to Beer's law; the optimum range for measurement in 1.0-cm cells was 0.05–0.5 p.p.m. The reagent was very sensitive and reacted with vanadium(V) to form a 1 : 1 complex. The apparent molar absorptivity of the vanadium complex was 5.95 × 10⁴ l mol^–1 cm^–1. Common anions and cations did not interfere. Interferences from copper, iron and nickel can be avoided by using the 8-hydroxyquinaldine extraction method. The proposed method is simple and sensitive and has been applied to the determination of vanadium in fuel oil and stack gas.