Magnetic solid phase extraction for the determination of Pb(II) and Cd(II) in high salt foods

The conventional method for the determination of heavy metals in food is acid digestion followed by atomic absorption spectrometry or induced coupled plasma mass spectrometry. However, for high salt foods, due to the strong matrix effect, the detection results are seriously inaccurate. In this work, sulfur-functionalized magnetic metal-organic frameworks (Fe₃O₄ @UiO-66-SH) were synthesized by coating Fe₃O₄ nanospheres with sulfydryl-functionalized UiO-66. The Fe₃O₄ @UiO-66-SH possesses both the magnetic properties of Fe₃O₄ and the diverse properties of metal-organic framework (MOF) in one material, which has the superiority of high surface area, easy-operation and strong adsorb ability with Pb (II) and Cd(II), is used to separate and determine Pb (II) and Cd(II) in high salt foods by magnetic solid phase extraction-induced plasma mass spectrometry. The detection limits (LODs) for Pb (II) and Cd(II) were 0.17 and 0.21 µg/kg, respectively, and the quantification limits (LOQs) were 0.56 and 0.66 µg/kg. Analyzing the certified reference material of soy sauce (CFAPA-QC1728–4, P41839) and estimating the spiked recoveries proved the accuracy and precision of the proposed method. The determined values agreed well with the reference values, and the recoveries for spiking sample varied from 85.8–100.5%.