Extraction-spectrophotometric Study of the Complex Formation in the System Vanadium(iv) – 4-nitrocatechol – Iodonitrotetrazolium Chloride – Water – Chloroform

The system vanadium(IV) – 4-nitrocatechol (NC) – iodonitrotetrazolium chloride (INT) water – chloroform is studied. The optimum conditions for complex formation and extraction into chloroform are found: pH=3.9-4.5 and reagent concentrations at least 2x10 mol l NC and 1.2x10 mol l INT. The composition of the ternary complex is found to be V(IV):NC:INT = 1:2:2 with maximum absorbance at 350 nm. Beer’s law is obeyed in the range from 0.1 μg ml to 3.0 μg ml V(IV). Molar absorptivity is found to be ε350=2.36x10 l mol cm. The following constants are determined: extraction constant lgKex=10.6, association constant lgβ=9.2 and recovery factor R=96%. The effect of foreign ions and reagents is studied as well.