Extraction of Vanadium(V) with Hydroxyamidine in the Presence of Adductants and its Spectrophotometric Determination with Diphenylcarbazide

The extraction of V(V) with N-hydroxy-N,N'-diphenylbenzamidine(HOA) in the presence of 100 adduct-forming substances, e.g. inorganic acids, carboxylic acids, phenols, aldehydes and amides from weakly acidic solution into chloroform has been studied. The molar absorptivities of the resultant adducts lie in the range of (1.5-7.8) × 103 lmol−1 cm−1 at λmax 575–635 nm. The most sensitive adductant, 4-nitro-phenol(NPhOH) has been chosen for detailed studies. The colour can be intensified at least 3-fold by the oxidation of diphenyl-carbazide to diphenylcarbazone with the extract in strong hydrochloric acid. The molar absorptivity of the resulting diphenylcarbazone in chloroform in terms of vanadium is 2.45 × 104 lmol−1 cm−1 at λmax 540 nm. The method is simple, rapid and reproducible and can be used for the detection of V(V) in water samples with a detection limit of 6 μg/1.