Síntesis y caracterización electroquímica de una membrana de poli(5Afen) para el desarrollo de electrodos modificados útiles para la determinación de neurotransmisores en presencia de ácido ascórbico Pubblico Deposited
En este trabajo de tesis doctoral se presenta la síntesis de la membrana de un polímero conductor, la poli(5-amino-1,10-fenantrolina), mediante la electropolimerización del monómero usando métodos potenciodinámicos y potenciostáticos sobre diferentes sustratos. La síntesis se caracterizó voltamperométricamente y se estudió el depósito de la membrana con los modelos que describen la formación de nuevas fases electroquímicas, mediante el análisis de los transitorios potenciostáticos de corriente. Se estudio la respuesta del electrodo modificado a la variación del pH, así como el comportamiento electroquímico de adrenalina y el ácido ascórbico en presencia de la membrana polimérica. El electrodo modificado se optimizó para obtener la mejor respuesta en presencia de adrenalina, en función de los parámetros de síntesis de la membrana. Así mismo, se empleó para determinar el punto de equivalencia en titulaciones potenciométricas ácido-base. Además, su empleo como sensor para la determinación voltamperométrica de adrenalina y dopamina, en presencia de ácido ascórbico. Validando el sensor para la determinación analítica de adrenalina y se utilizó para la determinación en un preparado farmacéutico.
The present work shows that the 5-amino-1,10-phenanthroline (5Aphen) molecule can be electrochemically polymerised, forming a conducting polymer, through potentiodynamic as well as potentiostatic methods onto different electrode substrates: 1) A composito electrode formed by with carbon paste in an epoxy matrix, 2) glassy carbon and 3) polycrystalline gold. Further. From the analysis of the experimental potentiostatic current-time j-t plots obtained using electrodes 2) and 3) it is shown that for both cases the formation mechanism of the polymer, (Poly5Afen) involves the simultaneous presence of an adsorption process, which seems predominant at times short enough to the start of the potential jump, and a three-dimensional 3D nucleation and growth process limited by the monomer diffusion toward the electrode’s interphase. The mechanism suggests that the growth of the polymer takes place via direct incorporation of the monomer species. Studies carried out varying the angular speed of the number a vitreous carbon 2) rotating disc electrode (RDE) showed that the limiting current increased directly proportional to the square root of the rotation frequency, as predicted by the Levich equation, thus indicating that the possible formation of intermediate oligomer species have a small effect on the polymer growth. It has been recognized that the synthesis method to produce conducting polymers plays a decisive role, because important features of the resulting membrane clearly depend on it. Variation of the membrane’s features such as the thickness, morphology and chemical properties will influence the overall response towards a given analyte present in solution. This work presents the results concerning the voltamperometric response generated during the oxidation of adrenaline using Pulse Differential Voltammetry, PDV, in the system composed by 0.1 M NaCl | carbon paste electrode, CPE, modified with poly(5Aphen) surface membranes, generated through potentiostatic and potentiodynamic means in solutions containing ascorbic acid, AA The results indicate that the electrochemical process to generate the membrane permits to control its thickness, improves the range of signal separation and the response of the adrenaline.
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