From the Shelf to the Particle: Preparation of Highly Organic-Functionalized Magnetic Composites via 4-Nitrophenyl Reactive Ester.

Preparation of chemically tunable magnetic nanoparticles (MNPs) is of great interest in many technological fields. Although numerous methods have been developed to prepare MNPs coated with functional organic moieties, most of them are complex, multistep, and involve the preparation of a specific ligand to be inserted on the particle surface. Herein, we describe the preparation of MNPs covered with reactive polymer poly(4-nitrophenyl methacrylate). The composite was prepared by the dispersion polymerization of 4-nitrophenyl methacrylate in the presence of magnetite nanoparticles stabilized by oleic acid. The novel material can be easily modified with amines to give chemically stable amide bonds without installation of pH-dependent features in the link. The extent of particle modification is readily monitored by the release of 4-nitrophenol from the polymer using UV-vis spectrophotometry. Good agreement between the degree of functionalization assessed by colorimetry and elemental analysis was obtained, and functionalization up to 3 mmol g-1 is easily attained. To illustrate the applicability of the method for catalyst development, we prepared imidazole-covered MNPs that accelerate the hydrolysis of a model organophosphate, with rate constants approximately 105-fold higher than the spontaneous hydrolysis. The catalyst can be recovered by a magnet and recycled without appreciable loss of catalytic activity.

Histamine functionalized magnetic nanoparticles (HIS-MNP) as a sorbent for thin film microextraction of endocrine disrupting compounds in aqueous samples and determination by high performance liquid chromatography-fluorescence detection.

This paper describes the development of a new method in which histamine-functionalized magnetic nanoparticles (HIS-MNP) are used as the extraction phase associated with thin-film microextraction and a 96-well plate system. This approach was applied to the determination of estrone, estriol, 17-ß-estradiol, 17α-ethynylestradiol, 4-octylphenol and 4-nonylphenol in aqueous samples by HPLC-FLD. Extraction and liquid desorption steps were optimized employing multivariate and univariate procedures. The optimum extraction conditions were 50 min of extraction time, no salt addition and sample pH 5. Liquid desorption was carried out for 30 min with 300 µL of acetonitrile:methanol (50:50 v/v). The quantification limits varied between 0.5 and 20 µg L-1. The method showed recovery values between 82 and 120%, and relative standard deviations varied from 0.1 to 13.6%.