Preparation And Analytical Applications Of Modified Electrode With Polymer Film

The aim of chemically modified electrodes (CMEs) is to carry out the molecular design on the electrode surface. In other words, to immobilize molecular, ion and polymer on the electrode surface and make the electrode specially chemical and electrochemical properties, so anticipant reactions can occur on its surface. CMEs make the electrode material abundant and enlarge its application in electrochemistry. Now, it has been of most active fields in electrochemistry and electroanalysis chemistry.This dissertation was concentrated on the use of various polymer materials and modification methods to prepare polymer modified electrodes and investigate their characterization and analytical application. The preparations of poly(amino black 10B) modified electrode, poly(eriochrome black T) modified electrode and poly(glutamic acid) modified electrode have been evaluated. Their micrographs, structure, properties and applications have been investigated by scanning electron microscopy (SEM), atomic force microscope (AFM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), differential pulse votammetry (DPV) and amperometric detection (AD). The main points of this dissertation are summarized as follows:1. Determination of dopamine on a poly(amino black 10B)/Nafion modified electrodeAmino black 10B is a weak acid dye with a large conjugate aroma ring, so it can be adsorbed physically on the surface of glass carbon electrode (GCE) byπ-πaction. But the capacity of physical adsorption is too hard to be controlled due to its poor adsorption and inherent unstable. To solve this problem, we prepared a modified electrode by electrochemical polymerization of amino black 10B on GCE, and covered by a film by Nafion. This poly(amino black 10B)/Nafion modified electrode is very sensitive and stable. The modification thickness can be controlled by electrochemical polymerization circles. The poly(amino black 10B) film was characterized by SEM, AFM and EIS. The electrode developed showed an excellent electrocatalytic ability towards dopamine oxidation. The redox peak current of dopamine increased linearly with the concentration in the range of 2.0×10-7～3.0×10-5 mol/L, and the detection limit (S/N=3) was 1.0×10-7 mol/L. Moreover, the modified electrode avoided the interference of ascorbic acid and exhibited good reproducibility. The modified electrode can be used for the determination of dopamine in the injections and serum with good recovery and reproducibility.2. Determination of vitamin B6 on a poly(amino black 10B) modified electrodeA poly(amino black 10B) modified electrode was fabricated by electrochemical polymerization of amino black 10B on GCE. The modified electrode shows good electrocatalytic activity to the oxidation of vitamin B6. DPV and AD were developed for the direct measurement of vitamin B6 with high sensitivity (5.0×10-8 mol/L). The modified electrode has many advantages such as fast response, good reproducibility, low cost and fabrication simplicity. The practical application of this modified electrode was demonstrated with vitamin B6 drugs determination3. Determination of nitrite on a poly(eriochrome black T) modified electrodeA poly(eriochrome black T) modified electrode was fabricated by electrochemical polymerization and was used to electrochemically determine nitrite. Due to the electrostatic interaction between the negatively-charged nitrite ions and poly(eriochrome black T) film, the poly(eriochrome black T) modified electrode exhibited enhanced electrocatalytic properties towards the reduction of nitrite, observing an improved peak current. The electron transfer coefficient is 0.735. The poly(eriochrome black T) modified electrode exhibited fast response towards nitrite with a detection limit of 1.0×10-8 mol/L and a linear range of 1.0×10-8～1.0×10-3 mol/L. The possible interferences from several common ions were tested. The developed modified electrode was also successfully applied to the determination of nitrite in pickle sample.4. Simultaneous determination of hydroquinone and catechol with poly(glutamic acid) modified electrodeGCE was modified with poly(glutamic acid) films by electrochemical polymerization of glutamic acid monomer. Poly(glutamic acid) films showed good adherence to the electrode surface. AFM images showed a fibres polymeric network film, allowing a high electron transfer. The performance of the modified electrode was characterized by CV and EIS. Poly(glutamic acid) modified electrode showed an excellent electrocatalytic ability towards the redox of hydroquinone and catechol, and a decrease of the overpotential and the improvement of the redox peak current was observed. Hydroquinone and catechol could be simultaneously analyzed on the modified electrode by CV and DPV techniques. Moreover, the modified electrode exhibited good reproducibility and long-time stability. It was successfully used to analyze hydroquinone and catechol in waste water samples.