A green cloud-point extraction-chromogenic system for vanadium determination

A cloud-point extraction-chromogenic system containing vanadium(V), 1-(2-thiazolylazo)-2-naphthol (TAN), H2O2 and Triton X-100 was investigated. The optimum conditions for vanadium extraction and spectrophotometric determination were found to be: concentrations of TAN and H2O2 (5 x 10(-5) and 3.0 x 10(-4) mol L-1, respectively), mass fraction of Triton X-100 (3%), acidity (5 x 10(-3) mol L-1 H2SO4), incubation time (60 min for hot plate or 10 min for microwave oven) and wavelength (607 nm). The composition of the extracted species was determined (V: TAN: O-2(2-) = 1: 1: 2), and the geometries of four possible structures, which differ by the coordination mode of O-2(2-), were optimized at the BLYP/cc-pVDZ level of theory. The UV-Vis spectra were calculated and compared with the experimental spectra. Species with two monodentate peroxide ligands are present in the extract, along with species containing one monodentate and one bidentate peroxide. The effect of foreign ions was studied, and the analytical characteristics of the developed procedure were determined. Spectral interference of copper(II) was observed; however, it can be corrected mathematically by measuring the absorbance at 580 and 610 nm. Iron(III) can be efficiently masked with HPO42-. The method was applied for analysis of various samples. Beer's law was obeyed up to 0.76 mu g mL(-1) of vanadium. The limits of detection (LOD) and determination (LOQ) and the molar absorptivity (epsilon(607)) were 1.4 ng mL(-1), 4.8 ng mL(-1) and 8.84 x 10(4) L mol(-1) cm(-1), respectively. (C) 2017 Elsevier B.V. All rights reserved.