Preparation of a monolithic magnetic stir bar for the determination of sulfonylurea herbicides coupled with HPLC

A hybrid material of metal organic frameworks (MOFs) and monoliths was developed and used for stir bar sorption extraction (SBSE) of five sulfonylurea herbicides. It was prepared in a glass tube (4 mm I.D.) by thermal polymerization using modified neodymium supermagnetic (Nd2Fe14B) powders as the component substrates, the organic polymerization solutions and ethyl cellulose as the adhesion agent. The prepared stir bar was characterized by scanning electron micrography (SEM) and X-ray diffraction (XRD). It was successfully applied for the determination of sulfonylurea herbicides in soil and lake water samples coupled with high-performance liquid chromatography (HPLC). The extraction and desorption factors affecting the performance of sulfonylurea herbicides were evaluated in detail. Under the optimum conditions, the extraction efficiency of the hybrid stir bar was obviously higher than the blank stir bar without UIO-66(Zr)-NH2. Linear ranges were 10–700 μg/L for thifensulfuron-methyl (TIM), amidosulfuron (AS) and metsulfuron-methyl (MSM) and 10–800 μg/L for sulfosulfuron (SSF) and tribenuron-methyl (TBM), respectively. The obtained detection limits were in the ranges of 0.04–0.84 μg/L with the recoveries of 68.8–98.1% for the real samples. The novel stir bar possessed excellent advantages of both supermagnetic performance and large specific surface areas in the presence of MOFs and monoliths, which was potentially an optimal adsorbent for environmental analysis.