Preparation of novel ionic-liquid-modified magnetic nanoparticles by a microwave-assisted method for sulfonylurea herbicides extraction.

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 R > 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 C 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%.