谷物新烟碱类农药残留电化学检测中基质效应的产生机制及消除策略研究

Neonicotinoid insecticides residues were widely existed in grain and accumulate in humans, hence, accurate detection of the trace residues is the important technical guarantee for food safety. The results showed that matrix effect is the primary cause for the poor accuracy in complex samples. During the preliminary study, the proposer found that the matrix effect in electrochemical sensing of neonicotinoid pesticides in grain was even higher than 90%, and speculated that the response signals were seriously reduced due to the polar molecules in food matrix which were adsorbed competitively on the surface of working electrode together with the biomacromolecules hindering the electron transfer of neoniconinoid pesticides. Based on this, this project plan to research on the right matrix effect through four steps. Firstly, the main components in grain matrix should be separated and the value of matrix effect will be evaluated. Combine with the change rules of adsorption equilibrium constant, dynamic rate constant, and electrochemical impedance, the formation mechanism will be revealed through two aspects including competitive adsorption and electron transfer hinder. Secondly, based on the various matrix components and their formation machanism of matrix effect, the matrix regulation methods including cleaning-up, dilution and desorption will be built to eliminate the matrix effect. Thirdly, reference probes such as electroactive molecules, other pesticides, metal materials will be researched to build ratiometric electrochemical sensor for interior correction. Finally, a novel electrochemical sensor for determination of neonicotinoid pesticide in grain is built and assessed. In brief, this project plan to provide new theoretic foundation and technique support to accurate detection of pesticide residue through the revelation of formation mechanism of matrix effect and hunting for the elimination strategy.

新烟碱类农药在谷物中广泛残留且对人体具有蓄积作用，准确检测其痕量残留是粮食安全的重要技术保障。研究表明，基质效应是复杂样品检测准确度低的主要原因。申请人前期研究发现，谷物中新烟碱类农药残留电化学传感检测的基质效应高达90%，推测基质中的极性分子等竞争吸附于电极表面以及生物大分子阻碍目标农药的电子传递，导致检测信号大幅降低。基于此，本项目拟分离谷物基质的主要成分，定量评价其基质效应，结合吸附平衡常数、动力学速率常数、电化学阻抗谱的变化规律，从竞争吸附及阻碍电子传递两方面揭示基质效应的产生机制；其次，针对不同基质成分及其基质效应产生机制建立净化、稀释、解吸等基质调控方法；再次，将电活性分子、其他农药、纳米金属作为参比探针，建立基于比率法的内部校正体系；最后，构建谷物中新烟碱类农药残留检测新方法。本项目通过揭示基质效应的产生机制探求其消除策略，预期为农药残留的准确检测提供新的理论依据及技术支撑。

谷物中农药残留广泛存在，且通过食物链进入人体对健康造成威胁，准确检测其痕量残留是粮食安全的重要技术保障。作为复杂样品检测准确度低的主要原因，基质效应的产生及消除研究是提高谷物中农药残留电化学传感技术检测性能的关键。基于此，本项目首先通过不同的提取、净化过程分离谷物基质的主要成分，定量评价其基质效应，乙腈-乙酸提取液中由于含有脂肪酸、脂溶性维生素、氨基酸等共存物质，基质减弱效应高达94.22%，采用PSA（乙二胺-N -丙基硅烷）吸附杂质后，基质效应达43.14%，结合C18和MgSO4（硫酸镁）对长链脂肪酸及乙酸等杂质的去除，基质效应降低至15.00%。之后，针对引起严重基质效应的共存干扰物构建特异性识别并分离杂质的基质调控方法，以超分子主体β-环糊精衍生物为功能单体、新烟碱类农药吡虫啉为模板分子、N,N-二甲基甲酰胺（DMF）与水的混合液为致孔剂合成分子印迹体系，将其滴涂于石墨烯修饰玻碳电极表面，制备成为新型工作电极，印迹因子达1.5，对目标农药具有良好的选择吸附能力，且对同类具有相似结构的新烟碱类农药具有特异性，增强了抗干扰能力。最后，针对难以去除和识别的基质成分，采用基于双信号的比率法进行内部校正，以二茂铁（Fc）、亚甲基蓝（MB）、硫堇（Th）、尼罗蓝（NB）为参比探针考察了其对比率信号的影响，NB由于与目标农药分离度高、交叉干扰小，将其作为参比探针，与基于单信号输出的传统方法相比，基于比率信号的内部校正法可将基质效应降低至7.24%。项目研究结果将为农药残留的准确检测提供创新性理论依据及技术指导，具有重要意义。