Determination of vanadium(V) based on its ternary complex with 2-(8-quinolylazo)-4,5-diphenylimidazole and hydrogen peroxide by high performance liquid chromatography

A method based on reversed-phase high performance liquid chromatographic separation in combination with spectrophotometric detection was developed for the determination of trace amounts of vanadium(V) as its ternary complex with 2-(8-quinolylazo)-4,5-diphenylimidazole (QAI) and hydrogen peroxide. Spectral and chromatographic behaviors of the ternary complex were investigated. The complex was formed in weekly acidic medium (pH 2.5-4.0) and separated on a Cosmosil 5C8-MS column with 58% (m/m) aqueous acetonitrile mobile phase containing 5.0 × 10^-3 mol kg^-1 acetate buffer (pH 3.5), 1.0 × 10^-4 mol kg^-1 tetrabutylammonium bromide and 1.0 × 10^-3 mol kg^-1 ethylenediaminetetraacetic acid and detected at 595 nm. The calibration curve was linear up to 35 ng for vanadium(V) in 25.0 mL of test solution at 0.001 absorbance unit full scale. The detection limit was 2 pg for vanadium(V) with 100 L injection. The method showed good accuracy, selectivity and sensitivity for the determination of vanadium(V) in environmental samples.