Preparation and Performance of an Estradiol Templated Magnetic Sphere of Molecularly Imprinted Cryogel

Abstract

An estradiol templated core-shell magnetic molecularly imprinted cryogel (MMIC) was synthesized to selectively extract and analyze estradiol in milk powder. The microsphere of Fe 3 O 4 @SiO 2 was firstly prepared on Fe 3 O 4 with ethyl silicate and 3-methyl propyl trimethoxy silane. Then the polymerization of α-methacrylic acid and ethylene glycol dimethyl acrylate was carried out on Fe 3 O 4 @SiO 2 at −20 °C for 24 h with estradiol as template. The morphology and microstructure of MMIC were investigated by transmission electron microscopy and infrared spectrogram. When used as chromatographic stationary phase, MMIC showed good selectivity and chromatographic performance for the template. Spiked milk powder samples were used to examine the adsorption capacity and selectivity of MMIC, giving recoveries of 92-101% and limit of detection 0.8-1.2 ng g −1 .Experimental results indicate good reproducibility with relative standard deviation from 2.2 to 4.5% (n = 3) at spiked levels of estradiol 10, 50, and 100 ng g -1 .Keywords: magnetic sphere, molecularly imprinted cryogel, estradiol, milk powder IntroductionSample preparation is of vital importance in an analysis for reducing the interference of impurities, concentrating the low abundant components, and improving the sensitivity and selectivity. Sample pretreatment occupies more than 60% of the entire time, while it presents poor reproducibility and accuracy. Thus, a sound sample pretreatment is crucial to guarantee the accuracy, reliability of the results, as well as the efficiency of analytical determination. Solid phase extraction (SPE) has widely been used in the extraction, purification, and enrichment of analytes in environmental, food, and biological samples. However, SPE cannot eliminate the interference of matrix in complex samples because the conventional adsorbents, such as normal, reverse, and ionic phase and other special adsorbents, have poor selectivity. Molecularly imprinted polymer (MIP) is a kind of inclusive compound prepared from template, monomer, and cross linker. There is a covalent bond or hydrogen bond or Van der Waals' force between template and polymer.2 When template molecule is removed, a specific cavity with binding sites complementary to the size, shape, and functional group of template is formed in the polymer.2 Molecularly imprinted polymers based solid phase extraction (MIP-SPE) can be implemented in selective separation, analysis, and preparation of high-purity target substance. MIP-SPE can achieve rapid and high efficiency of extraction of the analytes, because of high specific surface area and high mass transfer rate. 3,4Core-shell magnetic molecularly imprinted polymer (MMIP) is a new type of functional composite, the magnetic core (such as Fe 3 O 4 ) of which is covered with inorganic (SiO 2 , Al 2 O 3 , etc.) or organic (surfactant, polymer, etc.) layers. [5][6][7] The layer can be further modified with hydrophilic and/or biocompatible functional groups, including C=C, -NH-, -Br and sulfonyl, then dipole interaction of core is...