Synthesis and Application of a Novel Functionalized Magnetic Metal–Organic Framework Sorbent for Determination of Heavy Metal Ions in Fish Samples

This work describes the synthesis and application of a novel magnetic metal–organic framework (MOF) [(Fe3O4-dipyridylamine)/MIL-101(Fe)] to preconcentrate trace amounts of Cd(II), Pb(II), Co(II), and Ni(II) ions and their determination by flame atomic absorption spectrometry. A Box–Behnken design was used to find the parameters affecting the preconcentration procedure through response surface methodology. Three factors including sorption time, amount of the magnetic sorbent, and pH of sample were selected as affecting factors in the sorption step, and four factors including type, volume and concentration of the eluent as well as the elution time were selected in the elution step for the optimization study. These values were obtained as 30 mg, 11 min, 6.5, EDTA + HNO3, 4.3 mL, 0.7 mol L−l EDTA in 0.13 mol L−l HNO3 solution, 14 min, for amount of the magnetic sorbent, sorption time, pH of sample, type, volume, and concentration of the eluent, and elution time, respectively. The limits of detection (LODs) were 0.13, 0.75, 0.3, and 0.5 ng mL−1 for Cd(II), Pb(II), Co(II), and Ni(II) ions, respectively. The relative standard deviations (RSDs) of the method were less than 9.2% for five separate batch experiments for the determination of 30 µg L−1 of Cd(II), Pb(II), Co(II), and Ni(II) ions. The sorption capacity of [(Fe3O4-dipyridylamine)/MIL-101(Fe)] was 188 mg g−1 for cadmium, 201 mg g−1 for lead, 173 mg g−1 for cobalt and 154 mg g−1 for nickel. Finally, the magnetic MOF nanocomposite was successfully applied to rapid extraction of trace amounts of heavy metal ions in fish samples.