Ultrasonic-assisted supramolecular solvent liquid-liquid microextraction for inorganic chromium speciation in water samples and determination by uv-vis spectrophotometry

A simple and fast ultrasonic-assisted green supramolecular solvent liquid-liquid microextraction method (UA-SS-LLME) was developed for the determination of Cr(VI) and Cr(III). A Cr(VI) stock solution was complexed with 1,5-diphenylcarbazide (DPC) reagent to form a metal ligand reaction, followed by UV-Vis spectrophotometric analysis at 540 nm. Tetrahydrofuran (THF) and decanoic acids were also used for the microextraction of chromium speciation. Cr(III) was oxidized to Cr(VI) by using H₂SO₄ for the determination of total chromium. The Cr(III) concentration was calculated by subtracting the Cr(VI) concentration from total chromium. The parameters for sample volume, H₂ SO₄ concentration, DPC concentration, and ultrasonic bath time were optimized at 20 mL, 0.002 mol L^-1, 1.25×10^-4 mol L^-1, and 4 min, respectively. The interference effects of the matrix components were also examined. The limit of detection (LOD), limit of quantification (LOQ), enhancement factor, and the relative standard deviation were found at 0.79 μg L^-1, 2.64 μg L^-1, 50 and 2.40 %, respectively. The accuracy of the method was verified by analyzing two certified reference materials (TMDA-64.2 Fortified Lake Water and TMDA-53.3 Fortified Environmental Water). The proposed method was successfully used to the analysis of real environmental waters.