Extraction–photometric determination of vanadium in natural waters

The procedure for the extraction–photometric determination of vanadium from N-benzoyl-N-phenylhydroxylamine (N-BPHA) is improved for the analysis of natural waters. The dependence of the absorbance of extracts on the concentration of vanadium(V) in aqueous solution is linear in the range of 0–1500 μg/L and can be described by the equation A = (10.70 ± 0.02) × 10–4cV (μg/L). The molar absorption coefficient of the complex in chloroform is 5450 ±10 and its partition coefficient between the phases is equal to 26.1 ± 0.5. It is shown that vanadium in natural waters occurs in the free and bound forms. The prevailing anionic forms of vanadium(V) are, probably, free and the cationic species of vanadium(IV) are bound with organic components of natural waters. For the decomposition of the last named compounds, the authors recommend the oxidative digestion of samples by boiling with 1 mL conc. HClO4 to the appearance of fumes.