Quercetin-coated Fe3O4 nanoparticle sensors based on low-field NMR for determination and removal of Pb2+ and Cu2+ in biological samples

In this paper, we develop quercetin-coated Fe3O4 nanoparticles (QMNP(S)) as a sensor for the detection and removal of Pb2+ and Cu2+ based on low-field NMR. QMNP(S) were characterized by TEM, FTIR and XRD. The NMR sensor showed high selectivity toward Pb2+ or Cu2+. The standard curves for T-2-ion concentration showed good correlations, i.e., R-2 = 0.9912 for Pb2+ and 0.9983 for Cu2+; the linear ranges and the limits of detection were 4.8 x 10(-6)-1 x 10(-4) mol L-1 and 1.6 x 10(-6) mol L-1 for Pb2+, and 5.0 x 10(-6)-1 x 10(-4) mol L-1 and 2.0 x 10(-6) mol L-1 for Cu2+, respectively. The calculated maximum adsorption capacity was about 71 mg for Cu2+ and 68 mg for Pb2+ per gram of QMMP, which was superior to the results of some previous reports. The detection and removal of Pb2+ or Cu2+ was based on the coordination reaction between the NMR sensor of QMNPs and Pb2+ or Cu2+, which led to the aggregation of QMNPs. As a result, the proposed NMR sensor was successfully applied for the determination and removal of Pb2+ and Cu2+ in contaminated water and urine samples with excellent recoveries and high adsorbent capacities.