| Dopamine(DA) is an important catecholamine neurotransmitter compound that has been paid much attention recently. It plays a significant role in the function of the central nervous,renal, hormonal and cardiovascular system. Trace level measurement of DA has been a long-standing goal since the concentration change is associated with various diseases and disorders, such as Parkinson's disease, Alzheimer's disease, Huntington's disease, epilepsy,pheochromocytoma and so on. It is important to monitor DA sensitively and selectively not only for biomedical chemistry and neurochemistry research but also for diagnostic and pathological study purpose.Among the modified electrodes, organic polymer modified electrodes(OPMEs) prepared by electropolymerization have been drawn extensive attention due to their high selectivity,sensitivity and strong adherence to electrode surface, various OPMEs were studied for the electrocatalytic oxidation of DA.This thesis chiefly is the manufacture of electrochemical sensors, which based on glassy carbon electrodes modified by polydopamine(PDA) and p-aminobenzoic acids(p-ABA)composite membran,after degrading in alkali solution. We adopt cyclic voltammetry to detect dopamine using three electrodes system which reduced the interference of ascorbic acid and other interference substances and improved the applied performance of the sensor.The content of this thesis contains chiefly the following three parts:1. Electrochemical detection of DA based on porous PDA/GCE electrodeWe use electrochemical method to deposit dopamine onto a glassy carbon electrode, and then degraded in alkali solution to form porous PDA/GCE electrode as a dopamine sensor.Electrochemical means, scanning electron microscope(SEM) and x-ray photoelectron spectroscopy(XPS) were used to characterize films' formation, morphology and composition,respectively. Under optimal conditions, the PDA/GCE electrode was used to detect DA by cyclic voltammetry,scan voltage range is from-0.6 V to 0.6 V and scan rate is 80 m V/s. The sensor showed nice current responses by adding distinct concentrations of DA with a nice stability. The linear range of the detection of DA is from 0 to 30 ?M with a detection limit(S/N=3) of 2.2 ?M. But when the concentration of AA added over 50 ?M, which would interfere the determination of DA.2. Electrochemical detection of DA with PABA/GCE modified electrodeIn this system, we prepared a poly-(para amino benzoic acid, PABA) film electrode.The glassy carbon electrode was used as the substrate, and we use electrochemical deposition method to prepare the PABA polymer modified electrode, called after PABA/GCE.Electrochemical means and SEM were used for characterizing the modified films. The results of dopamine detection with PABA/GCE show that although the linear response of the modified electrode to the detection of dopamine is not high, it can effectively inhibit the concentration of 120 ?M ascorbic acid, which is superior to the PDA/GCE.3. The composite membrane electrode modified by porous poly(dopamine/p-amino benzoic acid) to improve the detection performance for dopamineIn this system, a composite film electrode was prepared by poly(dopamine/p-aminobenzoic acid) film for the electrochemical detection of dopamine. Cyclic voltammetry was used to prepare the PDA-PABA/GCE electrode, and then degraded in alkali solution to form porous PDA-PABA/GCE electrode, for PPM/GCE. Electrochemical methods,SEM and XPS were used for characterizing the composite film. The PPM/GCE was used to detect dopamine, it has a good linear response in the range of 0 ?M to 20 ?M, the correlation coefficient is 0.9961 and the lowest detectable limit is 0.7 ?M. The PPM/GCE electrode has better anti-interference to ascorbic acid or other substances than the PDA/GCE electrode and better sensitivity to DA than the PABA/GCE electrode. The good selectivity and high sensitivity reflect the innovation of this thesis. |
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