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Application of magnetic nano material in electrochemical analysis

Author: WangLu
Tutor: WangYang
School: Yangzhou University
Course: Analytical Chemistry
Keywords: Magnetite nanopartieles multi-walled carbon nanotubes lab-on-valve solid phaseextraction modified electrode β-cyclodextrin
CLC: O657.1
Type: Master's thesis
Year: 2013
Downloads: 42
Quote: 0
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Abstract


Nanomaterials attract more and more interest with the fast development of nanoseience and nanotechnology. Magnetite has good biocompatibility, strong superparamagnetic property, low toxicity, easy preparation and abundant functional groups on the surface.Various magnetic nanocomposites have been used in soild phase extraction, electrochemical sensor, biomolecule separation, and targeted drug delivery. The sequential injection lab-on-valve technology as the third generation of flow injection has the advantages of high injection speed, flexible injection volume size, simple apparatus, easy to use and so on. In this paper, integrating sequential injection lab-on valve and magnetite nanoparticles was proposed for analytical purpose, and the main study includes three parts:Chapter1Automated solid-phase extraction hyphenated to voltammetry for the determination of quercetin using magnetic nanoparticles and sequential injection lab-on-valve approachIn this study, an automated sequential injection lab-on-valve (SI-LOV) system was designed for the on-line matrix removal and preconcentration of quercetin. Octadecyl functionalized magnetic silica nanoparticles were prepared and packed into the microcolumn of the LOV as adsorbents. After being adsorbed through hydrophobic interaction, the analyte was eluted and subsequently introduced into the electrochemical flow cell by voltammetric quantification. The main parameters affectingthe performance of solid-phase extraction, such as sample pH and flow rate, eluent solution and volume, accumulation potential and accumulation time were investigated in detail. Under the optimum experimental conditions, a linear calibration curve was obtained in the range of0.01to10μmol/Lwith R2=0.9979. The relative standard deviation (RSD) for the determination of1.0μmol/L quercetin was found to be2.9%(n=11) along with a sampling frequency of40/h. The applicability and reliability of the automated method described here had been applied to the determination of quercetin in human urine and red wine samples through recovery experiments, and the obtained results were in good agreement with those obtained by the HPLC method.Chapter2A highly sensitive and automated method for the determination of hypoxanthine based on lab-on-valve approach using Fe3O4/MWCNTs/β-CD modified electrode A Fe3O4/multiwall carbon nanotubes/β-cyclodextrin (Fe3O4/MWCNTs/β-CD) modified electrode, for highly sensitive and automated hypoxanthine measurements, was developed in a sequential injectionlab-on-valve system. The electrochemical oxidation behavior of hypoxanthine was investigated in phosphate buffer solution by cyclic voltammetry and linear sweep voltammetry. The Fe3O4/MWCNTs/β-CD modified electrode exhibits preferably analytical characteristics in electrocatalytic activity towards the oxidation of hypoxanthine. Under optimized conditions, the log oxidation peak current intensity was proportional to log hypoxanthine concentration covering the range from0.05to10μmol/Lwith a correlation coefficient of0.9965. A detection limit of0.003μmol/Lwas achieved along with a sampling frequency of20/h. This hyphenated system offers some advantagesin terms of rapidness, sensitivity and ease of manipulation. Its further applications were utilized for thedetermination of hypoxanthine in meat samples.Chapter3Application of MWCNTs/Fe3O4modified electrode under inducing adsorption for rapid and sensitive detection of cadmium in a lab-on-valve systemA rapid and sensitive approach for the determination of trace levels of cadmium using stripping voltammetry coupled with a sequential injection lab-on-valve system was developed. The proposed method was based on the accumulation of cadmium on the multi-walled carbon nanotubes/Fe3O4nanoparticles modified electrode where iodide was used as the induced adsorption media. Different parameters such as supporting electrolyte and its pH, concentration of KI, amounts of modifier, accumulation potential, accumulation time, and flow rate were investigated to enhance the analytical performance. Under the optimum conditions, the signal intensity shows a linear relationship with the concentration of cadmium over the range of0.005to0.2μmol/L. A sampling frequency of24per hour and a detection limit of0.0027μmol/Lwere obtained with an accumulation time of120s. The relative standard deviation for11repeated measurements of0.01μmol/L cadmium was3.2%. The analytical use of the established method was validated by applying it to the determination of cadmium in natural waters samples and certified reference materials.

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CLC: > Mathematical sciences and chemical > Chemistry > Analytical Chemistry > Instrument analysis ( physics and physical chemistry ) > Electrochemical analysis
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