Electrocatalysis Research Of CLB And PBV Based On Nano-Au/（TiO₂）/Nafion Modified Electrodes

To date, various analytical methods have been reported for the analysis ofclenbuterol, including chromatography, immunoassay and other methods.Electrochemical sensor technology is a simple, fast and efficient process forclenbuterol detection, but rarely reported. Patent blue V (PBV) is a synthetic dye,which has been banned in China and the international community as a food dye. Thedetection methods for PBV focused on chromatography and spectroscopy, andelectrochemical methods rarely reported, and also its highest detection limit is2.0×108M.In this dissertation, the Nafion/Au (electrodeposit method), Nafion-Au (mixmethod) and Nafion/TiO2modified electrodes were prepared for detection ofclenbuterol and patent blue V. The XRD, UV-vis spectra, HRTEM, laser particleanalyzer and electrochemical methods were used to characterize the composite film,and electrochemical sensing mechanism were also be investigated. The modifiedelectrodes possess specific advantages such as simple fabrication, wide linear range,fast response, excellent reproducibility and long stability. The foundation forpractical application is studied. The main achievements in this thesis are summarizedas follows:1. GNPs with an approximate average diameter of~20nm were prepared by citratereduction of HAuCl4. The stable Nafion-Au colloids were immobilized on the glassycarbon electrode (GCE) for detection of β-agonist clenbuterol by electroanalysis. TheAu colloids prepared by a one-step electrodepositing onto GCE presented obviouselectrocatalytic activity, and the negatively charged Nafion film provided an efficientbarrier to negatively charged interfering compounds, resulting in accumulation ofpositively charged clenbuterol at Nafion film. The Nafion-Au colloids modifiedelectrode exhibits obvious electrocatalytic activity towards the redox of clenbuterol byenhancing peak current greatly with the linear calibration curve from8.0×107to1.0×105mol/L with a detection limit (1.0×107mol/L)(R=0.996). The recovery fordetecting clenbuterol (~10-6mol/L) in real human serum is up to98.19%. A relativestandard deviation of3.9%was obtained for six successive measurements of4×10-6 mol/L clenbuterol, suggesting good repeatability for clenbuterol detect. The modifiedelectrode was stored at4°C and measured intermittently for clenbuterol (4×10-6mol/L), and the current (IIa) still retained89%of its initial response after30days.2. A Nafion/Au composite film coated GCE was fabricated, and the electrochemicalbehavior of PBV on the Nafion/Au/GCE was investigated. We studied the variousinfluence parameters for sensitivity, such as pH value of solution, Nafionconcentration, PBV accumulation potential and accumulation time. On optimalconditions, a good linear relationship between anodic peak current and PBVconcentration was obtained in the range of5×10-8~8×10-6M with the detection limitof2.0×108M (R=0.997). The modified electrode shows high sensitivity andselectivity, and the mechanism is postulated that the excellent electrocatalytic activitycarried out by Au colloids and the enrichment of PBV onto Nafion.3. The Nafion/TiO2composite membranes modified glassy carbon electrode hasbeen successfully for the detection of PBV. The (B-R) buffer of pH=1.6was found tobe reasonable as a supporting electrolyte for detecting. At the optimized conditions,PBV showed a well-defined peak and good reversibility at0.8~0.9V using anaccumulation potential of0V. When the proposed methods were applied, a linearitywas achieved from1.6×10-8~5×10-6M with a detection limit of6.0×109M (R=0.998),which is higher than as reported. The modified electrode was stored at4°C and usedto measure intermittently for PBV, and the peak current nearly no changed after60days, A relative standard deviation of3.9%was obtained for ten successivemeasurements of1×10-5mol/L PBV. Since the application of nano-TiO2on theelectrode surface, the modified electrode on the adsorption capacity of PBV is greatlyreinforced, and thus it greatly improves the detection sensitivity. This method wassuccessfully employed with high precision and accuracy for estimating PBV.