Application Of Novel Organic/Inorganic Composites Electrochemical Sensor For The Detection Of Organic Pesticides

Health and food safety issues have been an important problem in social common concern. Due to the irregular management and use of pesticides, a serious of threat came about to food safety and agricultural ecological environment. Even have potential harm to human health. Pesticide residue problems have been attracted more and more attention. However, pesticide residue determination is very difficult due to the variety of pesticides and the complexity of pesticide residue analysis. Therefore, researching rapid, convenient, efficient and practical pesticide residue analysis methods has become a focus of current research, which has significantly theoretical and practical significance to protect the ecological environment and implement the strategy of food safety. Compared with the traditional methods, electrochemical method has been proposed as efficient alternative for the determination of pesticide residue due to its advantages of time-saving, low-cost, simple operation, sensitivity, selectivity, miniaturization, and real-time online detection. In resent years, researchers have put their efforts to improve the performances of electrochemical sensors. In our work, we fabricated a series of novel organic pesticide electrochemical sensors by adopting a variety of novel organic/inorganic composites and successfully applied in the electrochemical detection of different types of pesticides. In addition, its properties, such as stability, selectivity and sensitivity, and detection mechanism have been investigated. The proposed novel organic/inorganic electrochemical sensors have also been applied to the trace analysis of pesticide residues in real samples. Specific content is as follows:(1) A rapid, sensitive, and enzymeless organophosphorus pesticide methyl parathion (MP) electrochemical sensor was successfully fabricated by combining the benefits of high supramolecular recognition and enrichment capability of β-cyclodextrin (β-CD) and the electrocatalytic property of carboxylic acid functionalized single-walled carbon nanotubes (f-SWCNT). The modified electrode displayed excellent electrocatalytic activity towards MP. The calibration curves for MP were from ranges of0.002to0.02μg mL-1and0.02to17.5μg mL-1, with a low detection limit (S/N=3) of0.4ng mL-1after a very short preconcentration time for80s. The modified electrode also exhibited good reproducibility, good stability, and high sensitivity, and also successfully employed for the trace analysis of MP in vegetables samples, such as onions, lettuce, rape and spinach. This proposed electrochemical sensor can provide a promising candidate for the trace analysis of MP in agricultural and environmental.(2) Three facile carbon nanomaterials modified electrodes were successfully fabricated using the good electroconductivity and large specific surface area of novel carbon nanomaterials (single (multi)-walled carbon nanotubes (S(M)WCNTs) and electrochemically reduced graphene oxide (ER-GO)), and applied to detection organochlorine pesticide niclosamide (NA). A possible working mechanism for the electrochemical detection of NA was proposed. The experimental results showed that the ER-GO/GCE displayed lowest peak potential, highest sensitivity, best repeatability, reproducibility and peak shape as well as higher peak current response when compared with other modified electrodes. Additionally, ER-GO/GCE exhibited better linearity than S(M)WCNTs/GCE over ranges from0.020to23.1μM with the detection limit of6.6nM (S/N=3). The as-prepared ER-GO/GCE was successfully employed for real sample analysis with NA tablets, which can provide a promising candidate for the trace analysis of NA in agriculture.(3) On the basic of research (2), a novel facile, rapid and sensitive organochlorine pesticide NA electrochemical sensor was constructed by combining the benefits of low cost, specific surface area and strong adsorption capability of attapulgite (ATP) with fibrous structure and good water solubility and high surface activity of carboxylic acid-functionalized graphene (GR-COOH). It can be seen that the composite film had fibrous structure, which is benefit for electrochemical detection. The modified electrode is much cheaper and has better electrocatalytic activity towards NA, and also exhibited good reproducibility, good stability, and high sensitivity. The calibration curve for NA was obtained in both ranges of0.02to1.0μM and1.0to5.0M, with a low detection limit of4.6nM (S/N=3). The electrochemical sensor was also successfully applied to the trace analysis of NA in paddy water and NA tables.(4) Three facile and green electrosynthesis modified electrodes have been constructed by one step electropolymerization in aqueous microemulsion system, including poly(3,4-ethylenedioxythiophene)(PEDOT), poly(2,3-dihydrothieno[3,4-b][1,4]dioxin-2-yl) methanol)(PEDTM), and carboxylic group functionalized poly(3,4-ethylenedioxythiophene)(PC4-EDOT-COOH) modified electrodes. The electrochemical behavior of carbamate pesticide carbendazim (MBC) has been studied. In this work, it is found that different groups of functionalized modified materials had a great influence on the test object recognition. The recognition mechanism was proved by quantitative calculation. The experimental results showed that different groups functionalized PEDOT showed different degree of interaction with MBC. Attributing to high electron affinity of PC4-EDOT-COOH due to the electron-withdrawing effect of carboxyl group, PC4-EDOT-COOH/GCE is much easier to interact with MBC and exhibited a higher electroactivity for the trace detection of MBC with a lower detection limit of3.5nM (S/N=3) in comparison with the bare GCE, PEDOT/GCE and PEDTM/GCE. In addition, the as-fabricated PC4-EDOT-COOH film electrode was successfully employed for the trace level determination of MBC in paddy water and commercial juice.