▎ 摘　　要

This article investigates the applicability of an environmentally friendly and energy efficient deep eutectic solvents (DES) for indigotin blue dye (IBD) preconcentration prior to its quantification by a UV-Visible spectrophotometer. The adsorbent (UT-mGO) is made of Fe3O4, graphene oxide, urea and tetramethylammonium chloride. It was prepared via dispersing magnetic graphene oxide in a DES. The adsorbent was prepared fast and easy, without consumption of dangerous reagents. X-ray diffraction patterns show pure structures of components. FT-IR spectra show strong interaction between DES and mGO. In addition, a scanning electron microscope confirms that DES covered the surface of mGO homogeneously. Magnetic amount and surface property were characterized by an alternating gradient force magnetometer and Brunauer-Emmett-Teller, respectively. High surface area and enough magnetic property, as well as pi-pi and electrostatic interactions among analyte and adsorbent propose UT-mGO as a qualified candidate to preconcentrate IBD. Effective parameters including pH, adsorbent amount, adsorption time, eluent and desorption time were optimized. Under the optimized conditions, the method has the following figures of merit: (a) limit of detection of 1.5 x 10(-6) g L-1, (b) relative standard deviation (n = 7) of 3.49%, (c) preconcentration factor of 50 and (d) linearity of dynamic range of 1.0 x 10(-5) to 45 x 10(-5) g L-1. The adsorbent is not reusable but durable in six months. Isotherm model of Langmuir and kinetic model of pseudosecond-order fitted for the system. Delta H (-13.2 x 10(3) J mol(-1)), Delta S (5.38 J K-1 mol(-1)) and Delta G (-3.69 x 10(3) - +10.9 x 10(3) J mol(-1)) were calculated as thermodynamic parameters. The method was successfully applied for IBD preconcentration from three samples of fruit juices and three samples of jelly powders. (C) 2021 Published by Elsevier B.V.