Extract-photometric determination of vanadium(V) with 3-indole-acetohydroxamic acid

A spectrophotometric study has been carried out of the violet complex 3-indole-acetohydroxamic acid-vanadium extracted into a solution of trioctylmethyl-ammonium chloride in toluene [λmax 525 nm; e=5381 l mol−1 cm−1; stoichiometry 1:3 (metal:reagent)]. A new method for the extract-spectrophotometric determination of V5+ in the range of 2–7 μg/g is proposed and interferences by foreign ions were investigated. The method has been satisfactorily applied to the determination of vanadium(V) in fuel oil. The relative error is ±2.9%.