Ultrasonic-assisted supramolecular solvent liquid-liquid microextraction for determination of manganese and zinc at trace levels in vegetables: Experimental and theoretical studies

We present rapid, inexpensive and selective ultrasonic-assisted (UA) supramolecular solvent (Ss) liquid-liquid microextraction (LLME) method for the determination of Mn(II) and Zn(II) ions in vegetable samples. The presented method implies using of flame atomic absorption spectrometer (FAAS). We tried quercetin as a ligand to for Mn(II) and Zn(II) ions and observed complexation process in the solvent with pH = 8.0. The extraction of the obtained complexes was achieved by supramolecular solvent. This solvent was prepared with 1-decanol reverse micelles dispersed in tetrahydrofuran (THF)-water. Some experimental parameters (pH, ligand amount, THF volume, 1-decanol concentration, sonication time and matrix effect) were optimized to provide the most efficient extraction of Mn(II) and Zn(II) ions. Under optimized conditions, the working range, detection limit and sensitivity factor for Mn(II) ion were equal to 0.1-200 ng mL(-1), 0.035 ng mL(-1) and 107, respectively. The same parameters measured for Zn(II) ion were equal to 2-500 ng mL(-1), 0.6 ng mL(-1) and 88, respectively. Presented UA-Ss-LLME method was successfully applied for the extraction of Mn(II) and Zn(II) from certified vegetable samples prepared by microwave digestion. We also applied the density functional theory (DFT) to clarify atomistic details of interaction of Mn(II) and Zn(II) ions with quercetin. We computed structures, energies, electronic properties and quantum descriptors of metal ions-quercetin complexes. Calculated results are in reasonable agreement with the experimentally obtained data. (C) 2020 Elsevier B.V. All rights reserved.