Magnetic molecularly imprinted nanoparticles based on dendritic-grafting modification for determination of estrogens in plasma samples

In order to resolve the low imprinting efficiency of surface molecularly imprinted polymers (MIPs), a dendritic-grafting method introducing more functional groups was proposed to modify the SiO2-coated magnetic nanoparticles (SiO2-coated MNPs). And then magnetic MIPs (MMIPs) were obtained using 17-ethyl estradiol (EE2) as a pseudo template with dendronized SiO2-coated MNPs as the supporter, aiming to avoid residual template leakage and to increase the imprinting efficiency. The resulting MMIPs showed high adsorption capacity, quick binding kinetics and good selectivity for trace estrogens. Meanwhile, MMIPs were used as magnetic dispersive solid-phase extraction (MDSPE) materials coupled with HPLC-UV for the detection of trace estrogens. The amounts of three estrogens which were detected from the plasma samples of pregnant women were 5.28, 5.31 and 4.17 ng mL(-1), and the average recoveries were 87.8%, 93.1% and 90.6% for the spiked samples with RSDs in the range of 1.4-6.3%, respectively. All these results reveal that MMIPs as MDSPE materials has good applicability to selective extraction and separation of trace estrogens from complex samples. (C) 2012 Elsevier B.V. All rights reserved.