Preparation And Application Of Amino Acid/Chitosan Electrochemical Sensor

This paper described the preparation of two types of amino acids and chitosan modified glassy carbon electrode as electrochemical sensors. With potassium ferricyanide as the probe, eectrochemical impedance spectroscopy(EIS) and Cyclic voltammetry(CV) were used to investigate the electrochemical performances of the electrochemical sensors. Then, the electrochemical sensors were used to determination of copper (II), L-ascorbic acid and paracetamol. The effect of base solution, pH, scan rate, accumulation potential and accumulation time were investigated. The work of this paper was divided into three parts:In first part, a novel type of L-cysteine and chitosan modified glassy carbon electrode as an electrochemical sensor for determination of copper (Ⅱ) was fabricated in this paper. Eectrochemical impedance spectroscopy(EIS) and Cyclic voltammetry(CV) were used to investigate the electrochemical performances of the electrochemical sensor. This electrochemical sensor showed an excellent electrocatalytic activity towards copper(II) in in pH4.2 acetate buffer solution. The calibration curve for the linear scanning voltammetry (LSV) peak current increased linearly with increasing copper(Ⅱ) concentration in the range of 1.0×10^-8～1.0×10 ^-4mol/L, the linear equation was I(μA)=-1.192 + 0.4683c(μmol/L), a correlation coefficient of 0.99847 and the detection limit was found to be 5.3×10 -9mol/L. The modified electrode showed good stability, reproducibility and selectivity, with ability of simultaneous determination of copper(Ⅱ) and Lead (Ⅱ).In second part, the determination of L-ascorbic acid (AA) using a electrochemical sensor by modified glassy carbon electrode(GCE) with a mixture of L-cysteine and chitosan. Eectrochemical impedance spectroscopy(EIS) and Cyclic voltammetry(CV) were used to investigate the electrochemical performances of the electrochemical sensor. Kinetic parameters of AA on sensor such as diffusion coefficient and catalytic rate constant were determined by Chronoamperometry(CA). This electrochemical sensor showed an excellent electrocatalytic activity towards L-ascorbic acid in pH5.0 buffer solution of HAc-NaAc. The calibration curve for the linear scanning voltammetry (LSV) peak current increased linearly with increasing AA concentration in the range of 1.0×10^-5～2.0×10 ^-3mol/L and the detection limit was found to be 4.3×10 ^-6mol/L. The modified electrode showed good stability and reproducibility. The practical application of the electrochemical sensor was successfully applied for determining the concentration of AA in commercial vitamin C tablets.In third part, a novel type of L-serine and chitosan modified glassy carbon electrode (L-Ser/CS-GCE) as an electrochemical sensor for determination of paracetamol was fabricated. With potassium ferricyanide as the probe, electrochemical properties of this sensor were characterized via electrochemical impedance spectroscopy(EIS) and measured EIS data were fitted with an equivalent circuit to investigate the detailed information about the electrode/solution interface. The electrochemical behavior of paracetamol on L-Ser/CS-GCE was studied by Cyclic voltammetry(CV). This electrochemical sensor showed an excellent electrocatalytic activity for the oxidation of paracetamol in pH4.9 buffer solution of HAc-NaAc. Linear scan voltammetry (LSV) was used for determination of paracetamol. Peak current increased linearly with increasing paracetamol concentration in the range of 2.0×10^-6～1.0×10 ^-3mol/L and the detection limit was found to be 8.3×10-7mol/L. The electrochemical sensor showed good stability and reproducibility. The practical application of the electrochemical sensor was successfully applied for determining the concentration of paracetamol in commercial acetaminophen tablets.