“一锅法”制备氨基碳纳米管功能化磁性纳米粒子及其在谷物和蔬菜中苯氧羧酸类除草剂测定中的应用北大核心CSCD

有效萃取是分析复杂样品中苯氧羧酸类除草剂(PAs)残留的关键步骤。为此,该文利用“一锅法”水热技术快速、简便地制备了氨基碳纳米管功能化磁性纳米粒子(NH-CNTs@M)并作为磁固相萃取(MSPE)的萃取介质,用于萃取谷物和蔬菜样品中痕量PAs。研究利用多种手段对NH-CNTs@M的形貌、尺寸、磁性性质等进行了表征,结果表明FeO的粒径、氨基化碳纳米管的直径以及NH-CNTs@M的磁饱和值分别为30 nm、40 nm和44.2 emu/g。详细考察了制备条件和萃取参数对NH-CNTs@M/MSPE萃取性能的影响,结果表明,NH-CNTs@M/MSPE可通过π-π、疏水和氢键作用有效富集目标化合物,最佳萃取条件如下:吸附剂用量为30 mg,解吸溶剂为含2.0%(v/v)甲酸的乙腈溶液,吸附时间和解吸时间分别为8.0 min和3.0 min,基底pH值为6.0,不调节基底的离子强度。将NH-CNTs@M/MSPE与高效液相色谱-二极管阵列检测技术(HPLC-DAD)联用,建立了谷物和蔬菜中PAs的灵敏检测方法。谷物和蔬菜基质中苯氧羧酸类除草剂的检出限(LOD,S/N=3)分别为0.32~1.6μg/kg和0.53~1.6μg/kg,定量限(LOQ,S/N=10)分别为0.94~4.8μg/kg和1.6~4.8μg/kg。在两种实际样品中不同浓度下的加标回收率分别为73.1%~112%和72.3%~113%。与现有方法相比,所建方法具有萃取速度快、灵敏度高和环境友好等特点。

“One-pot” preparation of aminated carbon nanotube-modified magnetic nanoparticles and their application to the quantification of phenoxyacetic acid herbicides in cereal and vegetable samples

Phenoxyacetic acid herbicides (PAs) are widely used to control the growth of broad-leaf weeds in corn, tobacco, etc. The presence of PAs in plants even at low concentrations (at the ng/L to μg/L scale) may induce severe effects and lead to human health risks. Hence, a sensitive and reliable method for the determination of PAs at trace levels in cereals and vegetables is highly desired. Magnetic solid-phase extraction (MSPE) has attracted considerable attention on account of its benefits such as ease of separation, less solvent consumption, and good service life. In this study, aminated carbon nanotube-modified magnetic nanoparticles (NH₂-CNTs@M) were prepared by a convenient and simple “one-pot” strategy and employed as the adsorbent for the MSPE of PAs in crops. The fabrication procedure is very convenient. In detail, the aminated carbon nanotubes, Fe(Ⅱ), Fe(Ⅲ), and isopropanol were mixed in one pot with mechanical stirring and reacted for 2.0 h at 80 ℃. The spectroscopic properties, morphology, and magnetic properties of the synthetic adsorbent were characterized by Fourier Transform-infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results revealed that the size of Fe₃O₄, diameter of NH₂-CNTs, and the magnetic saturation values of NH₂-CNTs@M were 30 nm, 40 nm, and 44.2 emu/g, respectively. Additionally, the results of FT-IR and TEM characterization confirmed the successful fabrication of NH₂-CNTs@M by this “one-pot” hydrothermal approach. The NH₂-CNTs@M displayed satisfactory capability to capture PAs through π-π, hydrophobic, and hydrogen-bonding interactions. To realize the best extraction performance, the key parameters, including the amount of adsorbent, formic acid concentration in the eluent, adsorption and desorption time, sample pH, and ionic strength in the sample matrices, were inspected and studied in detail. The optimal conditions were as follows: amount of NH₂-CNTs@M, 30 mg; desorption solvent, 0.5 mL acetonitrile containing 2.0% (v/v) formic acid; adsorption and desorption times, 8.0 and 3.0 min, respectively; the sample pH was adjusted to 6.0, and no salt was added to the sample. Under the optimized extraction conditions, a sensitive, quick, and environmentally friendly method for the determination of the studied PAs in cereal and vegetable samples was established by the combination of NH₂-CNTs@M/MSPE with high performance liquid chromatography-diode array detection (HPLC-DAD). The enrichment factors for the studied PAs varied from 73 to 90. The limits of detection (S/N=3) for the PAs in the cereal and vegetable matrixes were in the ranges of 0.32-1.6 μg/kg and 0.53-1.6 μg/kg, respectively; and the limits of quantification (S/N=10) for the PAs in the cereal and vegetable matrixes were 0.94-4.8 μg/kg and 1.6-4.8 μg/kg. The developed method also showed wide linear ranges and good precision. Finally, the established NH₂-CNTs@M/MSPE-HPLC-DAD approach was applied to measure trace levels of PAs in cereals and vegetables, and good fortified recoveries (72.3% to 113%) and repeatability (RSDs below 10%) were obtained. The established approach has several advantages over the existing methods, such as high analytical speed, low LODs, and eco-friendliness.