Schematic illustration for synthesis of Fe3O4@SiO2@PIL, and extraction procedure of SUHs.

Ionic liquids immobilized on magnetic nanoparticles were prepared by an efficient microwave-assisted synthesis method, and the properties of the ionic liquids were tuned based on the aromatic functional modification of its anion through a simple metathesis reaction. The novel as-synthesized magnetic materials were characterized by various instrumental techniques. The magnetic nanoparticles have been utilized as adsorbents for the extraction of four sulfonylurea herbicides in tea samples, in combination with high-performance liquid chromatography analysis. Significant extraction parameters, including type and volume of desorption solvent, extraction time, amount of adsorbent, and ionic strength were investigated. Under the optimum conditions, good linearity was obtained in the concentration range of 1-150 μg/L for metsulfuron-methyl and bensulfuron-methyl, and 3-150 μg/L for sulfometuron-methyl and chlorimuron-ethyl, with correlation coefficients R2 > 0.9987. Low limits of detection were obtained ranging from 0.13 to 0.81 μg/L. The relative standard deviations were 1.8-3.9%. Comparisons of extraction efficiency with conventional solid-phase extraction equipped with a commercial C18 cartridge were performed. Results indicated that magnetic solid-phase extraction is simple, time-saving, efficient and inexpensive with the reusability of adsorbents. The proposed method has been successfully used to determine sulfonylurea herbicides from tea samples with satisfactory recoveries of 80.5-104.2%.

Novel poly(ionic liquids) were synthesized and immobilized on prepared magnetic nanoparticles, which were used to extract pesticides from fruit and vegetable samples by dispersive solid-phase extraction prior to high-performance liquid chromatography analysis. Compared with monomeric ionic liquids, poly(ionic liquids) have a larger effective contact area and higher viscosity, so they can achieve higher extraction efficiency and be used repeatedly without a decrease in analyte recovery. The immobilized poly(ionic liquids) were rapidly separated from the sample matrix, providing a simple approach for sample pretreatment. The nature and volume of the desorption solvent and amount of poly(ionic liquid)-modified magnetic material were optimized for the extraction process. Under optimum conditions, calibration curves were linear (R(2) > 0.9988) for pesticide concentrations in the range of 0.100-10.000 μg/L. The relative standard deviations for repeated determinations of the four analytes were 2.29-3.31%. The limits of detection and quantification were 0.29-0.88 and 0.97-2.93 μg/L, respectively. Our results demonstrate that the developed poly(ionic liquid)-modified material is an effective absorbent to extract pesticides from fruit and vegetable samples.

The optimum reaction conditions of ergosterol the conversion of to vitaminD2 were studied. A kinetic model on catalytic reaction of ergosterol by ultraviolet ray was proposed, which reflects the relationship of ergosterol, vitaminD2, previtaminD2, tachysterol, lumisterol and unknown-product with reaction time. The results of model analysis were verified by the results of experiments.