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Orientador: Lauro Tatsuo Kubota / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Química / Made available in DSpace on 2018-08-25T06:42:10Z (GMT). No. of bitstreams: 1 Bassetto_VictorCosta_M.pdf: 5997549 bytes, checksum: c28ca3fa1e15c81712b8aab83f1a7f0e (MD5) Previous issue date: 2014 / Resumo: Esta dissertação apresenta os desenvolvimentos realizados para a aplicação de ligas de cobre como detector de aminoácidos em cromatografia de íons. O trabalho apresenta o desenvolvimento desde estudos eletroquímicos fundamentais, onde a propriedade de metais como ouro, atual padrão para a técnica, e cobre são investigados frente aos aminoácidos. Neste passo a técnica de voltametria cíclica foi escolhida, pois permitiu explorar os vários fenômenos que ocorrem nos processos de óxido redução das moléculas sobre os eletrodos. Uma particularidade do trabalho é o eletrólito, que deve ser também a fase móvel da cromatografia, no caso hidróxido de sódio 0,15 mol L-1. Após o entendimento dos mecanismos básicos de óxido redução dos diferentes aminoácidos sobre os eletrodos de ouro e cobre em meio alcalino, este foi transferido para a aplicação em células de fluxo. Nessa fase observou-se que o cobre puro não apresentava suficiente resistência a corrosão que viabilizasse sua aplicação no sistema de cromatografia de íons. Sendo assim, optou-se pela aplicação do bronze como material sensor. O bronze escolhido possui 86% de cobre em sua composição e após comprovação através de estudos viu-se que o comportamento de óxido redução dos aminoácidos é similar ao cobre puro, porém com vantagens na resistência à corrosão. Também foram desenvolvidos, em conjunto com a University of Southampton, substratos de cobre que apresentam o efeito SERS. Este trabalho foi realizado para permitir a investigação das espécies intermediarias que se formam entre o aminoácido e o cobre (II) formado na superfície do eletrodo. Para a aplicação em fluxo foi necessário o desenvolvimento de pulsos de potencial para viabilizar a detecção dos aminoácidos e aumentar o tempo de vida útil do eletrodo. Após o desenvolvimento os pulsos foram otimizados e o sistema foi utilizado para detecção de valina em amostras de suplemento alimentar / Abstract: This dissertation presents the developments made for the application of copper alloys as detector for amino acids in ion chromatography. The work presents the development from fundamental electrochemistry studies, where properties of metals such as gold, current standard for the technique, and copper where tested against amino acids were performed through cyclic voltammetry technique. This method was chosen for the investigation because it allowed exploring the various phenomena that occur in the oxide reduction processes of the molecules on the electrodes. As a feature of the working electrolyte must also be the mobile phase of the chromatography, where 0.15 mol L-1 sodium hydroxide was used. After understanding the basic mechanisms of reduction and oxidation of the different amino acids over gold and copper electrodes in an alkaline medium, the knowledge obtained was transferred to the flow cells. At this time it was observed that the pure copper did not present sufficient resistance to corrosion, limiting its application in ion chromatography system. Thus, we chose the application of brass as sensor material. The chosen brass had 86% copper in its composition and demonstration through the studies, which its redox behavior of the amino acids is similar to those observed on pure copper, but with advantages in corrosion resistance. In addition, copper substrates showing the SERS effect was also developed in conjunction with the University of Southampton. This study was conducted to allow the investigation of intermediary species that are formed between the amino acid and copper (II) on the electrode surface. For application in flow was necessary to develop potential pulses to enable the detection of amino acids and increase the lifetime of the electrode. After the development of the pulses, it was optimized and the system was used for detection of valine in samples of food supplement / Mestrado / Quimica Analitica / Mestre em Química

This diploma thesis deals with the determination of creatinine using a combination of flow injection analysis (FIA) or high-performance liquid chromatography (HPLC) with pulse amperometry, an electrochemical technique based on the application of potential pulses on a gold working electrode. The determination was performed in a basic environment of borate buffer with creatinine concentration of 1∙10-4 mol∙l-1 . The lenght of the cleaning and activation pulse was optimized as well as the pH of the running buffer. A cleaning pulse of +1.8 V was first applied to the electrode for 100 ms, then an activation potential of -0.5 V was applied for 150 ms and then a measuring potential of +0.2 V for 300 ms. The optimal pH was selected as pH=9,4. Methanol and acetonitrile were added to the borate buffer to test whether creatinine could be determined in presence of these organic solvents and whether flow injection analysis could be transformed into HPLC. Methanol in the system caused peak deformation, acetonitrile did not cause the peak deformation in the system, at higher contents the baseline was destabilized. Furthermore, the calibration dependence in the range of concentrations from 2.5∙10-4 mol∙l-1 to 5∙10-6 mol ∙ l-1 was measured using PAD in combination with FIA. At higher concentrations, peaks splitted....