This work describes the synthesis and application of a novel magnetic metal-organic framework (MOF) [(Fe3O4-2,5-dimercapto-1,3,4-thiadiazole)/Cu3(benzene-1,3,5-tricarboxylate)2] to preconcentrate trace amounts of Cd(II), Pb(II), and Zn(II) ions. A Box–Behnken design was used to find the parameters affecting the preconcentration procedure through response surface methodology. Three variables including sorption time, amount of the magnetic sorbent, and sample pH were selected as affecting factors in the sorption step, and four parameters including type, volume, concentration of the eluent, and elution time were selected in the elution step for the optimization study. These values were 33 mg, 11 min, 5.7 EDTA, 4.3 mL, 0.64 mol L–l EDTA solution, 16 min, for amount of the magnetic sorbent, sorption time, sample pH, type, volume, and concentration of the eluent, and elution time, respectively. Following the sorption and elution steps, the ions were quantified by FAAS. The limits of detection were 0.10, 0.15, and 0.75 ng mL−1 for Cd(II), Zn(II), and Pb(II) ions, respectively. The relative standard deviations (RSD) of the method were less than 8.3% for five separate batch experiments in the determination of 25 μg L−1 of Cd(II), Zn(II), and Pb(II) ions. The sorption capacity of the magnetic MOF nanocomposite was 155 mg g−1 for Cd(II), 173 mg g−1 for Pb(II), and 190 mg g−1 for Zn(II). Finally, the magnetic MOF nanocomposite was successfully applied to rapidly extract trace amounts of heavy metal ions in baby food samples.
Determination of total arsenic in food samples by atomic absorption spectrophotometry with a graphite furnace after nickel ion added wet digestion.
