Study On The Application Of Chemically Modified Electrodes For Analysis Of Cadmium, Sudan Dyes And Gallic Acid

Electroanalytical method, which is simple, sensitive, reliable, repeatability and low costs, occupies an important place in analytical chemistry field. At present, electrochemical workers make unremitting efforts to look for simple, high sensitive electrochemical analysis methods. Chemically modified electrode is one of the most important topics of research on electroanalytical chemistry. To prepare the chemically modified electrodes, most often a thin film of selected chemical is either bound or coated onto the bare electrode surface to endow desirable properties of the film. To date, chemically modified electrodes have been extensively applied in the electrochemical determination of a wide variety of species as a sensitive and selective analytical method. In this paper, we continued to study the application of chemically modified electrodes for heavy metal cadmium ions and two kinds of biological small molecules analysis, and prepared four modified electrodes combined with the new nano-materials. Main research contents are as follows:1. Sensitive determination of Cd(Ⅱ) by square wave anodic stripping voltammetry with in situ bismuth-modified multiwalled carbon nanotubes doped carbon paste electrodesThis paper presents a new electrochemical method for the determination of Cd(Ⅱ) using a bismuth-modified multiwalled carbon nanotubes doped carbon paste electrode (Bi/MCNTs-CPE). Because of good electrical conductivity of MCNTs and excellent electroanalytical performance of bismuth film, the new electrode significantly enhances the sensitivity for the detection of Cd(Ⅱ) and exhibits superior performance in comparison to the bare carbon paste electrode, the bismuth-modified carbon paste electrode, and the multiwalled carbon nanotubes doped carbon paste electrode. Many parameters such as mass ratio of carbon paste and MCNTs, pH of measure solution, concentration of Bi(Ⅲ), preconcentration time, preconcentration potential, and operational parameters of square wave anodic stripping voltammetry were investigated. Under optimum conditions, the linear regression equation of Cd(Ⅱ) was ip=4.458c11.73(ip:μA, c:μg L-1, R=0.9983) from1.0to60μg L-1with a detection limit of0.3μg L-1. Finally, the Bi/MCNTs-CPE was successfully applied to the determination of Cd(Ⅱ) in tap water sample with satisfactory results. 2. Electrochemical determination of Sudan I using reduced graphene-modified glassy carbon electrodeReduced graphene (r-GO) was coated on the surfaces of glassy carbon electrode (GCE) to form a new and simple electrochemical sensor. Modified film electrode showed strong accumulation ability and excellent electrocatalytic activity for Sudan I. It increase significantly electrochemical oxidation signal of Sudan I. The experimental conditions such as amount of alcohol (%), accumulation time, pH of measure solution were optimized for the determination of Sudan I. Under optimum conditions, the linear regression equation of Sudan I was ip=0.3497+0.01525c (zp: μA, c:μg L-1, R=0.9982) from20to350μg L-1with a detection limit of17.8μg L-1.3. A novel conducting poly(p-aminobenzene sulfonic acid)-based electrochemical sensor for sensitive determination of Sudan I and application for detection in food stuffsIn the present work, a new method for the determination of Sudan I has been developed based on the conducting poly(p-aminobenzene sulfonic acid) film electrode. The new sensor showed strong accumulation ability and excellent electrocatalytic activity for Sudan I. Electrochemical oxidation signal of Sudan I was significantly increased. The experimental conditions such as amount of alcohol, pH of measure solution, accumulation time, and instrumental parameters for square wave anodic stripping voltammetry were optimized for the determination of Sudan I. Under optimum conditions, the linear regression equation of Sudan I was ip=1.868+0.1213c (ip:μA, c: μg L-1,R=0.9981) from1.00to500μg L-1with a detection limit of0.3μg L-1. Finally, this sensor was successfully employed to detect Sudan I in some hot chili and ketchup samples.4. Sensitive detection of gallic acid based on polyethyleneimine-functionalized graphene modified glassy carbon electrodeA new electrochemical sensor was developed based on polyethyleneimine-functionalized graphene oxide (PEI-rGO) modified glassy carbon electrode (PEI-rGO/GCE). The synthetic positive charged PEI-rGO had good electron transfer ability, large specific surface area, prominent biocompatibility and excellent adsorption. Its morphology and microstructure was characterized by scanning electron microscopy. The new electrode was firstly used for the detection of gallic acid, which exhibits superior performance in comparison to the bare glassy carbon electrode (GCE) and graphene oxide modified glassy carbon electrode (GO/GCE). The experimental conditions such as pH, adsorption time, and scan rate were optimized for the determination of gallic acid. Under optimum conditions, the linear regression equation of gallic acid was ip=12.76c-11.44(ip:μA, c:mg L-1, R=0.9887) from0.10to10mg L-1and ip=2.040c-110.5(ip:μA, c:mg L-1, R=0.9992) from10to50mg L-1with a detection limit (S/N=3) of0.07mg L-1. The method has been successfully applied to the determination of gallic acid in samples of green tea and black tea.