Ultrasonic-Assisted Micro Solid Phase Extraction of Arsenic on a New Ion-Imprinted Polymer Synthesized from Chitosan-Stabilized Pickering Emulsion in Water, Rice and Vegetable Samples

Pickering emulsion polymerization has been employed for the Ultrasonic assisted-micro solid phase extraction (UA-µSPE) of ultra trace arsenic species by a new magnetic ion imprinted polymer (MIIP) prior to hydride generation atomic absorption spectrometry. Hydride generation atomic absorption spectrometry (HGAAS) has been used due to its fast analysis time, simplicity, acceptable selectivity and inexpensive cost. 2-acetyl benzofuran thiosemicarbazone (2-ABT) as a new chelating agent and core- shell hydrophobic magnetic nanoparticles was synthesized and the polymerization was carried out at the presence of arsenic - ligand complex, crosslinker, monomer, initiator, stabilizing agent and water-oil emulsion magnetic carrier. The polymerization of IIP is usually carried out by covalent or non-covalent interactions between functional monomer and targeted template ion. The use of ultrasonic waves in polymerization process due to the cavitation effect and acoustic shock through physical phenomena such as micro-streaming and micro-turbulence can lead to dramatic increase in mass transfer, faster start-up and operative mixing and micro-mixing. Therefore, an improvement in the preconcentration efficiency of the method by decreasing the external and internal resistance of the mass transfer of the analyte is achieved. Introducing of magnetism to nano-adsorbents can provides a relatively rapid and easy procedure to separate them from aqueous phase by employing appropriate magnetic field. In addition to eliminating the centrifuge stage, deposition of polymer on these nanoparticles leads to an increase in surface area and ease of access to active polymer sites which can significantly improve the kinetic of metal absorption. In pickering emulsion polymerization method, solid colloidal particles act as stabilizers between two immiscible phases to form an emulsion and it is used to prepare of controlled size and stable nano-absorbent. In order to stabilize pickering emulsion polymerization in MIIP formulation, suitable stabilizers should be used. Chitosan with some unique properties such as biocompatibility, biodegradability and non-toxicity can be a good candidate for this purpose. Furthermore this biopolymer adsorbs heavy metals by chemisorption because of its amino and hydroxyl functional groups. In second step, the nanoparticles and polymers were characterized. The analytical parameters such were selected and optimozed by Plackett–Burman and Box–Behnken designs respectively. Linear dynamic range, detection limit and relative standard deviation were 0.01-85.000 µg.L-l, 0.003 µg.L-l, and 3.21%, respectively. The proposed preconcentration procedure was successfully applied to the determination of arsenic ion in a wide range of food samples with different and complex matrixes.本研究采用Pickering乳液聚合（Pickering emulsion polymerization），结合超声辅助微固相萃取（Ultrasonic assisted-micro solid phase extraction, UA-µSPE），以新型磁性离子印迹聚合物（magnetic ion imprinted polymer, MIIP）为萃取介质，对超痕量砷形态进行前处理，后续结合氢化物发生原子吸收光谱法（hydride generation atomic absorption spectrometry, HGAAS）完成检测。选用氢化物发生原子吸收光谱法的原因在于其分析速度快、操作简便、选择性优异且成本低廉。本研究合成了2-乙酰基苯并呋喃缩氨基硫脲（2-acetyl benzofuran thiosemicarbazone, 2-ABT）作为新型螯合剂，同时制备了核壳型疏水磁性纳米颗粒；聚合反应在砷-配体络合物、交联剂、单体、引发剂、稳定剂及水油乳液磁性载体的存在下完成。 离子印迹聚合物（ion imprinted polymer, IIP）的聚合通常通过功能单体与目标模板离子间的共价或非共价相互作用实现。聚合过程中引入超声波，借助空化效应、声冲击以及微流、微湍流等物理现象，可显著强化传质效率、加快反应启动并优化混合与微观混合效果，进而降低分析物传质的内外阻力，提升方法的预富集性能。将磁性引入纳米吸附剂，可通过施加合适磁场实现水相中吸附剂的快速便捷分离。相较于离心分离步骤，在纳米颗粒表面负载聚合物不仅能够增大比表面积，还可使活性聚合物位点更易被接触，显著提升金属吸附动力学性能。在Pickering乳液聚合法中，固体胶体颗粒作为稳定剂作用于两相不混溶体系以形成乳液，该方法可用于制备尺寸可控且稳定的纳米吸附剂。为稳定磁性离子印迹聚合物体系中的Pickering乳液聚合，需选用合适的稳定剂。壳聚糖（chitosan）因生物相容性、生物可降解性及无毒等独特特性，可作为该类稳定剂的优良选择；此外，该生物聚合物凭借其氨基与羟基官能团，可通过化学吸附作用捕获重金属。 第二步，对纳米颗粒与聚合物进行表征。通过Plackett–Burman设计与Box–Behnken设计分别筛选并优化分析参数。方法的线性动态范围为0.01~85.000 μg·L⁻¹，检出限为0.003 μg·L⁻¹，相对标准偏差为3.21%。所提出的预富集方法已成功应用于多种复杂基质食品样品中砷离子的测定。