| Food additives are kinds of non-available nutrient substance including synthetic andnatural materials which have been added into food to improve the colour and taste, and preventfood rancidity. Nowdays, food additives mainly include foaming agent, antioxidant,preservative, colorant, thickener and so on. As a kind of food additives, antioxidant such asbutylated hydroxyanisole, propyl gallate and tert-butylhydroquinone could retard theautoxidation that may lead to rancidity. Antioxidant has been used widely in baked and friedfood products to prolong the quality guarantee period. With the addition, many people foundthat the safety of these artificial phenolic substances was questioned, because they may result ina loss of nourishment, and produce toxic substances harmful to human health. In differentcountries, the application of antioxidant is limited by different rules. For example, in China,Australia and America, the addition in food of antioxidant is permitted to be a maximum limitof200mg/Kg, but in Japan and the European Union, which is banned. Therefore, the reliabledetermination of antioxidant is important to human health and food safety.Nowadays, the reported detection technique for antioxidant mainly includeshigh-performance liquid chromatography (HPLC), gas chromatography (GC) and UV-visiblephotometry. These methods usually require complex pretreatment steps, expensiveinstrumental equipment and long response times and so on. Thus, it is necessary for us toexplore a sensitive and fast analytical technique for the detection of antioxidant in food.In the work, we constructed three types of electrochemical sensors based on variousnanocomposites modified glass carbon electrode and the specificity target recognition ofmolecularly imprinted technique. These sensors could be applied in the detection of butylatedhydroxyanisole, propyl gallate and tert-butylhydroquinone, respectively. Also these fabricatedsensors all exhibited excellent performance such as low detection limits, wide liner range, goodrepeatability and high selectivity. They have been applied in the determination of antioxidant inreal samples successfully.The contents of this work were listed as following:1. We developed an novel electrochemical sensor for the detection of BHA in foodstuffsbased on the good conductivity of GR-PB composites which were used to modify the glass carbon electrode and molecularly imprinted technique. The cooperation of GR and PBimproved both the current response and the detection sensitivity of the constructed sensor. Inthe preparation process of MIPs, BHA and pyrrole were selected as the template molecule andfunctional monomer, respectively. They were electropolymerized on the surface of theelectrode modified by GR-PB. The constructed imprinted electrochemical sensor wascharacterized by scanning electron microscopy (SEM), electrochemical impedancespectroscopy (EIS), cyclic voltammetry (CV) and chronoamperometry. The linear detectionrange of the sensor was from9×10-8mol/L to7×10-5mol/L, with the limit of detection (LOD)of7.63×10-8mol/L (S/N=3). Also the sensor showed excellent reproducibility, repeatability andstability. Meantime, this sensor has been used successfully in the determination of BHA in realsamples.2. In this work, a novel molecularly imprinted electrochemical sensor based onAuNPs@SiO2core-shell imprinted composites as recognition element and grapheneoxide-manganese dioxide (GO-MnO2)/ionic liquid-multiwalled carbon nanotubes(IL-MWCNTs) double amplified materials modified glassy carbon electrode (GCE) for thedetection of tert-butylhydroquinone (TBHQ) in foodstuffs was developed. We synthesized onekind of novel molecularly imprinted polymers (MIPs) that were TBHQ-imprinted core-shellcomposites of gold nanoparticles (AuNPs) as core structure and SiO2as shell material(AuNPs@SiO2-MIPs). AuNPs have large specific surface area and high conductivity and silicashell has excellent biocompatibility and affinity, which increased the amount of binding sitesand enhanced the imprinting effect of the proposed sensor. The template molecules (TBHQ)were imprinted on the surface of AuNPs through the adsorption and the hydrogen bondsbetween template molecules and silica film. The mechanism of fabrication and some factorsaffecting the performance of the sensor have been investigated. The sensor was characterizedby cyclic voltammetry (CV), scanning electron microscopy (SEM) and chronoamperometry.Under the optimized conditions, the linear range of the sensor was from2×10-8mol/L to1×10-5mol/L, with the limit of detection (LOD) of1.8×10-8mol/L (S/N=3). The proposed sensorexhibited high selectivity and sensitivity, excellent stability and good reproducibility towardsTBHQ. It was applied to determine TBHQ in real samples successfully, and the acceptablerecovery manifested its feasibility for practical application. 3. A novel molecularly imprinted electrochemical sensor for propyl gallate (PG)determination was developed by electropolymerization of an o-phenylenediamine membrane inthe presence of template molecules on an glassy carbon electrode surface modified by PtAubimetallic nanoparticles-encapsulated graphene-carbon nanotubes hybrid nanomaterials(PtAu-GrCNTs). The modified electrodes were characterized by cyclic voltammetry, scanningelectron microscope, x-ray diffraction and chronoamperometry. Besides, experimentalparameters such as scan cycles, deposition time, the ratio of template molecule to functionalmonomer, and extraction time were optimized. The results revealed the PtAu-GrCNTsnanocomposites demonstrated performance improvements and the MIPs sensor showed gooddynamic linear response in PG binding measurements (the linear range was from7×10-8mol/Lto1×10-5mol/L with the limit of detection of6.81×10-9mol/L). The relevant experimentsillustrated the developed sensor had the advantages in its high binding affinity and superbselectivity towards PG, good reproducibility and long-term stability. Additionally, the MIPssensor was also successfully applied to quantify PG in food samples. |
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