A modified catalytic-spectrometric method for the determination of ultra trace vanadium in phosphoric acid

A modified method is used for the specific and sensitive determination of vanadium in commercial phosphoric acid. The method is based on kinetic reaction as follows: vanadium in the sample is oxidized to vanadium(V) by peroxodisulfate under heating, followed by a selective extraction using the highly selective N-benzoyl-N-phenylhydroxylamine (BPHA) chelate and chloroform as the most efficient extractant of vanadium(V)-BPHA complex, then chloroform is evaporated. Kinetic method by the catalytic effect of vanadium(V) on the oxidation of gallic acid by potassium peroxodisulfate at 35 degrees C is used for spectrophotometric determination of vanadium at 415 nm after 45 min. The pre-separation of vanadium has resulted in interference-free determination. Results were compared with those of atomic absorption spectrometry.