Poly(deep eutectic solvent)-functionalized magnetic metal-organic framework composites coupled with solid-phase extraction for the selective separation of cationic dyes.

Novel polymeric deep eutectic solvents (PDES) based on 3-acrylamidopropyl trimethylammonium chloride/D-sorbitol functionalized amino-magnetic (Fe3O4NH2) metal-organic framework (HKUST-1-MOF) composites (Fe3O4NH2@HKUST-1@PDES) were synthesized and characterized by field emission transmission electron microscope (FE-SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), fourier transform infrared spectrometry (FT-IR), thermal gravimetric analysis (TGA), vibrating sample magnetometer (VSM) and zeta potentials. Then the composites were firstly utilized to selectively separate malachite green (MG) and crystal violet (CV) coupled with magnetic solid-phase extraction (MSPE). A response surface methodology (RSM) based on Latin hypercube sampling (LHS) was selected to analytically optimize the extraction parameters including initial concentration of dyes, extraction time, pH value and extraction temperature. The maximum extraction amount and optimal extraction conditions predicted by the RSM model matched well with the actual experimental results, and the extraction amount was 966.93 mg g-1 for MG and 788.90 mg g-1 for CV,respectively. The results indicated that the model possessed higher calculation accuracy through analyzing fewer sample points, thereby achieving theoretical prediction of extraction amount and conditions and being a prefect supplementary to actual experiments. The electrostatic interaction between the composites and cationic dyes played the main roll in the extraction process. The proposed extraction method exhibited lower limit of detection (98.19 ng mL-1 for MG and 23.97 ng mL-1 for CV) and preeminent precision (RSD ˂ 0.4%). Spiked recoveries of fish samples at three spiking levers ranged from 89.43% to 100.65% for MG and 95.29%-98.03% for CV. All results highlighted the excellent potential of Fe3O4NH2@HKUST-1@PDES-MSPE strategy in selective separation of cationic dyes in complex medium.