| This research is mainly divided into two parts.(1)Solid-phase extraction using magnetic core-shell-shell molecularly imprinted nano-sorbent followed by spectrophotometric determination of malachite green residues in aquatic products. Malachite green(MG)is a synthetic trip-phenyl methane dye usually used for the dyeing of leather, cotton, silk, and wool. In the 1930 s, it was used as fungicide and biocide in aquaculture industry for treatment or prevention of parasitic and external fungal infections in fish. However, researches have shown that MG is teratogenic and carcinogenic. Therefore, many countries and areas, including European, the United States, and China have been banned its use in aquaculture. But, due to the high efficacy and low cost,MG is still used in some parts of the world. Therefore, development of a sensitive and effective method is of great significance for trace determination of MG in aquatic products and related samples. In this study, a novel magnetic core-shell-shell nanocomposite sorbent was fabricated by covalently bonding silica-wrapped Fe3O4 nanoparticleswith graphene oxide nanosheets, and then the resultant magnetic graphene oxide was coated with molecularly imprinted polydopamine via self-polymerization of dopamine at the presence of template malachite MG. In the optimized experimental conditions, good linearity in the range of 5.0 – 400 ng m L-1was obtained with a correlation coefficient of 0.9996 and a limit of detection of 1.5 ng m L-1. The nano-sorbent was successfully applied to selective solid-phase extraction coupled with spectrophotometric determination of MG in fish and environmental water samples with recoveries ranged from 94.0 % to101.2 % and relative standard deviations of less than 4.3 %.(2) The fabrication and application of ronidazole electrochemical sensor based on graphene/boron doped molecularly imprinted polymer modified carbon paste electrode. Ronidazole(RNZ) is antiprotozoal drug from the nitromidazole family with special effect on anti-parasit(turkeys histomoniasis, trichuriasis) and antibacteria. In addition, RNZ is also used as feed addictives to improve the rate of feed conversion and increase the weight of the animals. However, RNZ contains a nitroimidazole ring, which might cause directly or indirectly harm to the health of humans. Hence, it's crucial to establish a quick, simple,convenient, and effective analytical method for detection of RNZ on behalf of the human's food safety. In this study, a new RNZ electrochemical sensor based on graphene/molecularly imprintedpolymer(MIP) film modified carbon paste electrode(CPE) was developed, which was prepared by electrodeposition of 4-aminobenzoic acid as functional monomer and 3-aminophenyl boronic acid as dopant on a graphene coated CPE using potentiodynamic cycling of potential in the presence of RNZ. Under optimal experimental conditions, the peak currents by differential pulse voltammetry were found to vary linearly with RNZ concentrations in the range of 0.2 to 250 ?mol L-1 with a detection limit of 0.067 ?mol L-1. This sensor was successfully employed to detect RNZ in egg, milk powder and honey samples with acceptable recoveries of 92.6 % to 101.9 % and RSD of 2.95 % to4.26 %. |
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