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  • Title: [Preparation of sulfonic acid-functionalized polymeric ionic liquid-based magnetic adsorbent and its applications to diquat extraction].
    Author: Guo B, Yang Z, Sun Y, He L.
    Journal: Se Pu; 2022 Oct; 40(10):921-928. PubMed ID: 36222255.
    Abstract:
    In terms of the structure of polar pollutants, the design and development of new materials that can interact with target analytes is vital for effective extraction. Diquat is a broad-spectrum herbicide with strong toxicity. It is sprayed during the growing process of vegetables because of its high efficiency and low cost. Furthermore, diquat is a polar and basic cationic organic compound. Therefore, it is necessary to develop adsorbents that can form strong interaction with diquat to extract it from complex vegetable samples. In this study, sulfonic acid-functionalized ionic liquid, 1-vinyl-3-propyl(3'-sulfonate) imidazolium chloride ([VPImi-SO3H][Cl]), was synthesized through the reaction of 1-vinylimidazole and 1,3-propanesultone and characterized using nuclear magnetic-resonance spectroscopy. The resulting [VPImi-SO3H][Cl] was then immobilized on the surface of vinyl-modified magnetic silica to obtain poly-(1-vinyl-3-propyl(3'-sulfonate) imidazolium chloride)-modified magnetic nanoparticles (Poly([VPImi-SO3H][Cl])-MP) via free radical polymerization between vinyl groups. The structure, morphology and magnetism of the obtained Poly([VPImi-SO3H][Cl])-MP were characterized using Fourier transform infrared spectroscopy, scanning electron microscope, vibrating sample magnetometer, and thermogravimetric analysis. The characterization results indicated that the Poly([VPImi-SO3H][Cl])-MP was synthesized with strong magnetic properties. Poly([VPImi-SO3H][Cl])-MP as magnetic adsorbent exhibited a different pH response to anion and cation. With the increase in solution pH, the adsorption efficiency of Poly([VPImi-SO3H][Cl])-MP for anionic dye amaranth decreased; whereas, the adsorption efficiency for cationic dye, methylene blue, increased. Under a high pH condition, sulfonic acid groups on the surface of Poly([VPImi-SO3H][Cl])-MP existed in the form of -SO3-. Thus, the adsorption efficiency of Poly([VPImi-SO3H][Cl])-MP for methylene blue could reach 95.2% due to the strong electrostatic attraction between adsorbent and positively charged methylene blue; whereas, negatively charged amaranth could hardly be adsorbed due to the electrostatic repulsion between adsorbent and amaranth. The above results showed sulfonic acid modification endowed Poly([VPImi-SO3H][Cl])-MP with abundant negative charges at certain pH conditions. Thus, the extraction can be achieved by the strong electrostatic attraction between negatively charged Poly([VPImi-SO3H][Cl])-MP and positively charged diquat. Using green vegetables as the sample matrix and magnetic solid-phase extraction as extraction model, the extraction performance of Poly([VPImi-SO3H][Cl])-MP for diquat was studied. Some extraction parameters affecting the extraction efficiency, such as solution pH, adsorbent amount, adsorption time, desorption solvent and its volume, and desorption time were optimized using the single factor experiment method. Under the optimized extraction conditions (30 mg of adsorbent, 15 min of adsorption time, 40 μL of ammonia, 600 μL of acetonitrile-formic acid (9∶1, v/v) as desorption solvent, 1 min of desorption time), the performance, and applicability of the proposed method were investigated by combining magnetic solid-phase extraction, high performance liquid chromatography, and UV-visible detector. Good linearity was observed at contents ranging from 0.2 to 20 μg/g with a correlation coefficient (r) of 0.9981. The limit of detection and limit of quantification based on the signal-to-noise ratio of 3∶1 and 10∶1 were 0.09 and 0.2 μg/g, respectively. The spiked recoveries at three levels of 0.5, 1.0, and 2.5 μg/g were obtained in the range of 82.7%-97.5% with the relative standard deviations of 2.8%-5.0% (n=3). The results showed that the sulfonic acid-functionalized Poly([VPImi-SO3H][Cl])-MP could be employed as a magnetic adsorbent for the quick and effective extraction of diquat, and the proposed method could be used for the determination of diquat from green vegetable samples. It could be anticipated that Poly([VPImi-SO3H][Cl])-MP could be used as an adsorbent for extracting other cationic polar pollutants by adjusting the solution pH. This work provides a new way to construct adsorbents for extracting polar pollutants. 有效萃取复杂食品样品中的极性污染物是实现其准确测定的瓶颈,也是食品安全分析的难点。针对污染物的结构特点,设计和发展能与之产生特定作用的新型材料是高效萃取的关键。敌草快是一种广谱性除草剂,为碱性的阳离子有机化合物。该文以1-乙烯基咪唑和1,3-丙磺酸内酯为原料合成了磺酸功能化的离子液体,通过自由基聚合反应,将其固载至磁性纳米颗粒表面,得到磺酸功能化的聚(1-乙烯基-3-丙基磺酸基咪唑氯盐)修饰的磁性纳米颗粒(Poly([VPImi-SO3H][Cl])-MP)。采用红外光谱、扫描电镜、振动样品磁强计和热重分析等对其结构、形貌和磁性进行了表征。将其作为磁性固相萃取的吸附剂,萃取青菜中的敌草快。磺酸基的功能化使Poly([VPImi-SO3H][Cl])-MP的表面在一定pH下带有丰富的负电荷,与敌草快之间产生强的静电吸引作用,可实现对敌草快的有效萃取。对影响萃取效率的各种参数如溶液pH、吸附剂质量、吸附时间、解吸剂种类和体积等进行了优化。在优化条件下,结合磁性固相萃取和高效液相色谱技术,对方法的性能及适用性进行了考察。敌草快在0.2~20 μg/g内具有良好的线性(r=0.9981),检出限(S/N=3)和定量限(S/N=10)分别为0.09 μg/g和0.2 μg/g; 3个水平(0.5、1.0和2.5 μg/g)下的加标回收率为82.7%~97.5%,相对标准偏差为2.8%~5.0%(n=3)。结果表明,磺酸功能化的Poly([VPImi-SO3H][Cl])-MP能快速、有效地萃取敌草快,建立的方法能用于青菜中敌草快的准确测定。
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