Liquid-Liquid Extraction-Chromogenic System for Vanadium(V) Based on 4-(2-thiazolylazo)orcinol (TAO) and Aliquat 336

The quaternary ammonium salt Aliquat 336 (A336; R 4 N + Cl - ) and the azo dye 4-(2-thiazolylazo)orcinol (ТАО) were examined as constituents of a water-isobutanol extraction-chromogenic system for vanadium(V). Under the optimum conditions ( c TAO = 1.6´10 –3 mol dm –3 , c A336 = 1.3´10 –2 mol dm –3 and pH 5.0), vanadium(V) is extracted as a ternary complex which can be represented by the formula (R 4 N + )[VO 2 (TAO 2 - )]. The key extraction-spectrophotometric characteristics were determined. The interfering effect of foreign ions was studied as well. The wavelength of maximum absorption ( λ max ), molar absorptivity ( e max ), constant of extraction ( K ex ) and fraction extracted ( E ) were found to be λ = 547 nm, e = 3.1×10 4 dm 3 mol –1 cm –1 , Log K ex = 2.8 and E = 90.2%, respectively. Beer’s law was obeyed in the range of 0.084–2.0 mg cm –3 and the limit of detection was 25 ng cm –3 of vanadium(V).