An environmentally friendly cloud point extraction–spectrophotometric determination of trace vanadium using a novel reagent

• Published in: Journal of molecular liquids Vol. 334; p. 116086
• Main Authors: Milcheva, Nikolina P., Genç, Fatma, Racheva, Petya V., Delchev, Vassil B., Andruch, Vasil, Gavazov, Kiril B.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-07-2021
• Subjects: Azo dye; Cloud point extraction; DFT calculations; Green analytical procedure index; Hydrogen peroxide; Vanadium; Cloud point extraction; Hydrogen peroxide; Azo dye; DFT calculations; Vanadium; Green analytical procedure index
• ISSN: 0167-7322; 1873-3166
• DOI: 10.1016/j.molliq.2021.116086

•A CPE-chromogenic system for total vanadium determination was studied.•The system involves a novel commercially available reagent, HTAR.•HTAR was investigated by both theoretical (B3LYP) and experimental approaches.•The developed procedure is simple, cheap, reliable, and environmentally friendly.•Greenness of the procedure was evaluated by GAPI.
A simple, low-cost, and green cloud point extraction (CPE) procedure was developed for the preconcentration of traces of vanadium as a preliminary step for its spectrophotometric determination. Vanadium(V) was complexed with H2O2 and a novel commercially available reagent, 6-hexyl-4-(2-thiazolylazo)-resorcinol (HTAR), which was preliminary investigated by both theoretical (B3LYP/6-311++G**) and experimental approaches. The ternary complex was then extracted into a small volume of a surfactant-rich phase (Triton X-100). The experimental conditions for total vanadium determination, optimized by the one‐factor‐at‐a‐time method, were found: H2O2 concentration (1.8 × 10−4 mol L−1), HTAR concentration (6.4 × 10−5 mol L−1), acidity (7 × 10−3 mol L−1 H2SO4), mass fraction of the surfactant (2%), incubation time (25 min) and wavelength (582 nm). The linear range, limit of detection, molar absorption coefficient and enrichment factor were calculated to be 2.6–510 ng mL−1, 0.8 ng mL−1, 1.66 × 105 L mol−1 cm−1, and 10.4, respectively. The composition of the extracted complex was V:HTAR:O22− = 1:1:2, which corresponds to a formula [VV(HL)(O2)2], where HL− is the monoprotonated HTAR. The effect of foreign ions was studied, and the accuracy of the proposed procedure was verified by an analysis of an environmental matrix reference material (TM-15.3; Canadian fortified lake water containing 14.2 ng mL−1 of vanadium) and spent silica-supported catalysts. The “greenness” of the developed method was evaluated using the Green Analytical Procedure Index (GAPI).