No description available.

Master of Science - Chemistry / Complexation of CrIII was studied using the ligand 2, 2’ Bipyridyl (Bpy). Potentiometric titration was used in the modelling of CrIII-Bpy complexes and establishment of complex stability constants by use of ESTA software package. Investigation of the mechanism involved in the voltammetric determination of chromium by adsorptive cathodic stripping voltammetry (AdCSV) showed different behavior of chromium in 0.1 M ammonium buffer when compared to a neutral electrolyte (0.1 M sodium nitrate). Alternating current voltammetry (ACV) showed evidence of Bpy adsorption on the electrode surface (HMDE) whereas CrIII did not show any adsorption evidence but complexes of CrIII-Bpy were also adsorbed onto the electrode. Cyclic voltammogram (CV) of Bpy exhibits a reversible process and CrIII was characterized by a quasireversible process. CrIII-Bpy is investigated here as a model metal-ligand system used in analytical procedure. A set of generalized requirements for the determination of CrIII by AdCSV is proposed and discussed. It is anticipated that the generalized requirements will be applicable to any metal-ligand system used by that analytical technique. It is assumed that it should lead to an “educated” choice of a suitable ligand in order to increase selectivity and improve the detection limit in ultra trace analysis (ppb-ppt levels) by AdCSV.

A large part of the work presented in this thesis describes the development and use of a novel electrochemical detector designed to allow the electrochemical characterisation of compounds in flowing solution by means of cyclic voltammetry. The detector was microprocessor controlled, which provides digital generation of the potential waveform and collection of data for subsequent analysis. Microdisk working electrodes are employed to permit both thermodynamic and kinetically controlled processes to be studied under steady-state conditions in flowing solutions without the distortion or hysteresis normally encountered with larger sized electrodes. The effect of electrode size, potential scan rate, and solution flow rate are studied extensively with the oxidation of ferrocene used as an example of a thermodynamically controlled process and a series of catecholamines as examples of a kinetically controlled process. The performance of the detector was best demonstrated when used as a HPLC post-column detector. The 3-dimensional chromatovoltammograms obtained allow on-line characterisation of each fraction as it elutes from the column. The rest of the work presented in this thesis involves the study of the oxidative degradation pathway of dithranol. The oxidative pathway was shown to involve a complex free radical mechanism, dependent on the presence of both oxygen and, in particular light. The pathway is further complicated by the fact that dithranol may exist in either a keto or enol form, the enol being most susceptible to oxidation. A likely mechanism is proposed from studies performed with cyclic voltammetry and controlled potential electrolysis, then defined by subsequent kinetic studies.

Orientador: Jarbas Jose Rodrigues Rohwedder / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-10T02:35:04Z (GMT). No. of bitstreams: 1 Killner_MarioHenriqueMontazzolli_M.pdf: 2163718 bytes, checksum: 57b0452d9c198120c39d7c2faffd08e3 (MD5) Previous issue date: 2007 / Resumo: O presente trabalho descreve o desenvolvimento de um sistema voltametrico microfluidico, de um potenciostato de baixo custo e de um programa computacional para controle do potenciostato e aquisição de dados. O sistema voltamétrico microfluídico foi confeccionado empregando dois fotopolímeros, sendo um sólido e outro líquido. Foi também avaliado o uso de uma resina acrílica. Técnica de litografia utilizando radiação UVA foi empregada para a confecção dos protótipos. O fotopolímero líquido, a base de uretano-acrilato, apresentou as melhores características como flexibilidade, fácil manuseio e boa selagem dos canais analíticos. Estes canais foram confeccionados com largura de 600 mm e profundidade de 100 mm. O eletrodo de trabalho foi construido empregando um fio de platina de 75 mm de diâmetro e 1,5 mm de comprimento. Uma agulha de aço inox de 13 mm de comprimento e 0,45 mm de diametro foi empregada como eletrodo auxiliar e um fio de prata de 600 mm de diâmetro e 2,0 mm de comprimento recoberto com cloreto de prata foi utilizado na construção do eletrodo de referência. Os resultados de voltametria cíclica para soluções de diferentes concentrações de FeK4(CN)6 obtidos utilizando o sistema desenvolvido foram semelhantes aqueles obtidos empregando um potenciostato comercial. A determinação de Pb(II) em uma amostra certificada (452,2 mg L) apresentou um erro relativo de -3,9% e desvio relativo de 2,0% (n=3) empregando voltametria de redissolução anódica com varredura de onda quadrada / Abstract: The present work describes the development of a microfluidic voltammetric system, a low cost potentiostat, and a software used for data acquisition and control of the potentiostat. The microfluidic voltammetric system was formed using two photopolymers, one solid and one liquid. In addition, the use of an acrylic resin was evaluated. The photolitography using UVA radiation was used for the fabrication of prototypes. The liquid polymer of urethane-acrylate showed better characteristics such as flexibility, easy manipulation and good sealing of the analytical channels. The analytical channels were 600 mm width and 100 mm depth. The work electrode was made of a platinum wire of 75 mm of diameter and 1,5 mm of length. A stainless steel needle 13 mm long and with 0,45 mm of diameter was employed as auxiliary electrode and a silver wire of 600 mm of diameter and 2,0 mm long covered with AgCl was employed as reference electrode. The results obtained using Cyclic Voltammetry for solutions of different concentrations of FeK4(CN)6 and the developed system were similar to those obtained using a commercial potentiostat. The determination of Pb(II) in a certificated sample of water (452,2 mg L) showed a relative error of ¿3,9% and a relative standard deviation of 2,0% (n=3) employing anodic stripping voltammetry and square wave potential scan / Mestrado / Quimica Analitica / Mestre em Química

No description available.

Contaminated aquatic sediments pose health risks to fish, wildlife, and humans and can limit recreational and economic uses of surface waters. Technical and cost effective in situ approaches for sediment management and remediation have been identified as a research need. Subaqueous in situ capping is a promising remedial approach; however, little is known regarding its impact on underlying sedimentary processes and the feasibility of bioaugmented caps at sites subject to contaminated groundwater seepage. This work specifically addresses (1) the impact of capping on biogeochemical processes at the sediment-water interface, (2) the ability and degree to which indigenous sediment microorganisms colonize an overlying cap, (3) the effect of advective flow direction on redox conditions within a cap, (4) natural contaminant bioattenuation processes within capped sediment, and (5) limitations toward a functional bioreactive in situ cap. Laboratory-scale experiments with capped sediment columns demonstrated that emplacement of a sand-based in situ cap induced an upward, vertical shift of terminal electron accepting processes into the overlying cap while simultaneously conserving redox stratification. Upflow conditions simulating a groundwater seep compressed anaerobic processes towards the cap-water interface. Microorganisms indigenous to the underlying sediment colonized cap material and spatial population differences generally reflected redox stratification. Downflow of oxic surface water through the cap, simulating tidally-induced recharge, created fully oxic conditions within the cap, demonstrating that flow direction strongly contributes to redox conditions. Experiments simulating capped sediment subject to contaminated groundwater seepage revealed a reduction of natural bioattenuation processes with time, stemming from the elimination of labile organic matter deposition to the sediment and a subsequent lack of electron donor. Thus, parent contaminants within groundwater seeps will be subject to minimal biotransformations within the sediment before entering a reducing cap. A bioreactive cap, inoculated with microorganisms capable of reductive dehalogenation, was established to reductively dechlorinate tetrachloroethene present in the groundwater; however electron donor amendments to sediment effluent were required to achieve complete dechlorination of tetrachloroethene to non-toxic ethene. Results from this work improve understanding of biogeochemical and bioattenuation processes within capped aquatic sediments and should aid in the development of active capping technologies.

As características produtivas e reprodutivas de colônias de abelhas são influenciadas pelo clima e a disponibilidade de alimento na região em que são criadas ou mantidas, assim, o armazenamento de mel e pólen, a postura da rainha e a ocupação dos favos estão sujeitos às variações sazonais. O presente estudo foi desenvolvido no apiário do Departamento de Entomologia e Acarologia, no campus Luiz de Queiróz, ESALQ/USP, no município de Piracicaba, em área contendo plantas frutíferas, ornamentais e fragmento de mata nativa. O objetivo foi verificar quais e a qualidade ambiental dos recursos políniferos usados pelas abelhas A. mellifera durante as quatro estações do ano (2010-2011) 5 colmeias de Apis mellifera L., durante 7 dias consecutivos. Em cada uma das estações verificaram-se os tipos polínicos presentes nas massas de pólen (bolotas), as características físicoquímicas (lipídeos, fibras e proteína) e os metais (Zn 2+; Cu 2+; Pb 2+ ; Cd 2+). Para preparação das amostras para palinologia adotou-se o método da acetólise (ERDTMAN, 1952); para a determinação de metais foi utilizada a técnica de Voltametria de Redissolução Anódica de Pulso Diferencial (DPASV); para proteína foi utilizado o Método de Bradford, 1976 e os outros parâmetros foram baseados em métodos convencionais. A análise quantitativa foi realizada por meio da contagem sucessiva de 900 grãos por amostra e agrupados por espécies botânicas e/ou tipos polínicos. Com base nos resultados obtidos pode-se afirmar que as abelhas utilizaram as plantas de diversos tipos presentes na área utilizaram as plantas ruderais como fonte de coleta de pólen para manutenção de suas colônias. Acrescentando à sua dieta o pólen de outras plantas arbóreas, arbustivas e herbáceas, conforme o recurso tornou-se disponível na área (Eucalyptus sp, Leucaena sp., Morus nigra, Cecropia sp., e os tipos polínicos Arecaceae, Asteraceae e Myrcia). Os parâmetros físico-químicos sofreram interferência direta com os dados meteorológicos o que pode ser comprovado a partir das analise feita na matriz de correlação e analise de fatores. As analise de elementos traço Zinco; Cobre e Chumbo apresentaram valores superiores aos estabelecidos para ingestão diária em alimento, mas não existe nenhum valor como indicador no ambiente. Cádmio não ultrapassou os limites estabelecidos para consumo, mas teve alto valor encontrado no pólen. Esses valores encontrados podem estar associados ao local onde o apiário encontra-se com varias fontes poluentes como trafego intenso de veículos na principal via de acesso, estação de tratamento de água e esgoto, áreas agrícolas, industriais e residências. / The productive and reproductive characteristics of bees colonies are influenced by climate and food availability in the location they are raised or kept, and for that, the storage of honey and pollen, the queens posture and the occupation of honeycombs are linked to seasonal variation. The present study was developed in the apiary at Entomology and Acarology Department, in Luiz de Queiróz campus, ESALQ/USP, located at Piracicaba city, in a place with fructiferous, ornamental and plants and fragments of native vegetation. The aim was the verification of quality and which pollinic ambient resources were used by Apis mellifera L bees, during the four seasons of the year (2010-2011), in 7 consecutive days. At each season the pollic type where verified in the pollen masses (pollen balls) as well as the physical chemistry (lipids, fibers and proteins) and for metals (Zn 2+; Cu 2+; Pb 2+ ; Cd 2+). The method adopted for the samples preparation for the PALINOLOGIA was acetolysis (ERDTMAN, 1952); for metals determination the Volumetric REDISSOLUÇAO ANÓDICA DE PULSO DIFERENCIAL technique were used, and for protein the Bradford Method (1976). The other parameters where analised based in conventional methods. The quantitative analyses was done by successive counting of 900 pollen grains per sample, assembled by botanical species or pollinic types. Based in the results obtained, it can be affirmed that bees used several types of plants presents in the area, using the urban plants as pollen source to keep their colonies. The bees adds to their diet other pollen from arborous, shrub and herbaceous plants as they become available in the area ( Eucalyptus sp., Leucaena sp.,Morus nigra, Cecropia sp., and the pollinic types Arecaceae, Asteraceae and Myrcia). The physical chemistry parameters suffered direct influence of the meteorological data, which can be proved from the analyses made on the correlation matrix and factor analyses. The analysis for Zinc, Copper and Lead traces shown superior values of what is acceptable to ingest in daily meal, but there are no values established as environmental indicators. Cadmium had high levels found in pollen, although it did not surpass the established limits for consumption. The values founds can be associated to the place where the apiary is located, which has pollutant sources as intense car traffic in the main access via, water and sewer station treatment, agricultural and industrial areas and residences.

As características produtivas e reprodutivas de colônias de abelhas são influenciadas pelo clima e a disponibilidade de alimento na região em que são criadas ou mantidas, assim, o armazenamento de mel e pólen, a postura da rainha e a ocupação dos favos estão sujeitos às variações sazonais. O presente estudo foi desenvolvido no apiário do Departamento de Entomologia e Acarologia, no campus Luiz de Queiróz, ESALQ/USP, no município de Piracicaba, em área contendo plantas frutíferas, ornamentais e fragmento de mata nativa. O objetivo foi verificar quais e a qualidade ambiental dos recursos políniferos usados pelas abelhas A. mellifera durante as quatro estações do ano (2010-2011) 5 colmeias de Apis mellifera L., durante 7 dias consecutivos. Em cada uma das estações verificaram-se os tipos polínicos presentes nas massas de pólen (bolotas), as características físicoquímicas (lipídeos, fibras e proteína) e os metais (Zn 2+; Cu 2+; Pb 2+ ; Cd 2+). Para preparação das amostras para palinologia adotou-se o método da acetólise (ERDTMAN, 1952); para a determinação de metais foi utilizada a técnica de Voltametria de Redissolução Anódica de Pulso Diferencial (DPASV); para proteína foi utilizado o Método de Bradford, 1976 e os outros parâmetros foram baseados em métodos convencionais. A análise quantitativa foi realizada por meio da contagem sucessiva de 900 grãos por amostra e agrupados por espécies botânicas e/ou tipos polínicos. Com base nos resultados obtidos pode-se afirmar que as abelhas utilizaram as plantas de diversos tipos presentes na área utilizaram as plantas ruderais como fonte de coleta de pólen para manutenção de suas colônias. Acrescentando à sua dieta o pólen de outras plantas arbóreas, arbustivas e herbáceas, conforme o recurso tornou-se disponível na área (Eucalyptus sp, Leucaena sp., Morus nigra, Cecropia sp., e os tipos polínicos Arecaceae, Asteraceae e Myrcia). Os parâmetros físico-químicos sofreram interferência direta com os dados meteorológicos o que pode ser comprovado a partir das analise feita na matriz de correlação e analise de fatores. As analise de elementos traço Zinco; Cobre e Chumbo apresentaram valores superiores aos estabelecidos para ingestão diária em alimento, mas não existe nenhum valor como indicador no ambiente. Cádmio não ultrapassou os limites estabelecidos para consumo, mas teve alto valor encontrado no pólen. Esses valores encontrados podem estar associados ao local onde o apiário encontra-se com varias fontes poluentes como trafego intenso de veículos na principal via de acesso, estação de tratamento de água e esgoto, áreas agrícolas, industriais e residências. / The productive and reproductive characteristics of bees colonies are influenced by climate and food availability in the location they are raised or kept, and for that, the storage of honey and pollen, the queens posture and the occupation of honeycombs are linked to seasonal variation. The present study was developed in the apiary at Entomology and Acarology Department, in Luiz de Queiróz campus, ESALQ/USP, located at Piracicaba city, in a place with fructiferous, ornamental and plants and fragments of native vegetation. The aim was the verification of quality and which pollinic ambient resources were used by Apis mellifera L bees, during the four seasons of the year (2010-2011), in 7 consecutive days. At each season the pollic type where verified in the pollen masses (pollen balls) as well as the physical chemistry (lipids, fibers and proteins) and for metals (Zn 2+; Cu 2+; Pb 2+ ; Cd 2+). The method adopted for the samples preparation for the PALINOLOGIA was acetolysis (ERDTMAN, 1952); for metals determination the Volumetric REDISSOLUÇAO ANÓDICA DE PULSO DIFERENCIAL technique were used, and for protein the Bradford Method (1976). The other parameters where analised based in conventional methods. The quantitative analyses was done by successive counting of 900 pollen grains per sample, assembled by botanical species or pollinic types. Based in the results obtained, it can be affirmed that bees used several types of plants presents in the area, using the urban plants as pollen source to keep their colonies. The bees adds to their diet other pollen from arborous, shrub and herbaceous plants as they become available in the area ( Eucalyptus sp., Leucaena sp.,Morus nigra, Cecropia sp., and the pollinic types Arecaceae, Asteraceae and Myrcia). The physical chemistry parameters suffered direct influence of the meteorological data, which can be proved from the analyses made on the correlation matrix and factor analyses. The analysis for Zinc, Copper and Lead traces shown superior values of what is acceptable to ingest in daily meal, but there are no values established as environmental indicators. Cadmium had high levels found in pollen, although it did not surpass the established limits for consumption. The values founds can be associated to the place where the apiary is located, which has pollutant sources as intense car traffic in the main access via, water and sewer station treatment, agricultural and industrial areas and residences.

The objective of the research was to investigate proton-coupled electron transfer (PCET) reactions involving antioxidants to gain insight into the detailed mechanisms of glutathione (GSH), Trolox, and α-tocopherol (α-TOH). PCET reactions are complex redox reactions that transfer electrons and protons sequentially or in concert. These reactions are ubiquitous in natural or artificial processes that produce electrochemical energy that is extractable as electricity or as chemical fuels of high energy content. Examples of processes based on PCET are photosynthesis, respiration, nitrogen fixation, carbon dioxide reduction, redox fuel cells, and artificial photosynthesis. Antioxidants were selected as a PCET model to understand the coupling between proton transfer (PT) and electron transfer (ET) in order to elucidate structure-reactivity relationships under different experimental conditions. PCET reactions were studied with a set of electrochemical techniques to propose a preliminary mechanism that could be validated with digital simulations matching the electrochemical response. In some cases, other analytical techniques were used to aid in the system characterization. This thesis presents the results and discussion of the effects of oxidant-base pairs on the mediated oxidation of GSH, the -2e-/-H+ process of Trolox in aqueous and nonaqueous solvents with various pH values, and the particle collision electrolysis of α-tocopherol in oil-in-water emulsion droplets on an ultramicroelectrode. Ultimately our goal was to determine the kinetic and thermodynamic factors that control PCET reactions so that they can be applied in designing artificial systems for the production of energy using more abundant reagents with lower cost and better yields.

Neste trabalho foram estudadas as potencialidades eletroanalíticas de um material híbrido condutor baseado em acetato de celulose e grafite com eletrodeposição de filme condutor de Azul da Prússia (CA/G/PB) como sensor para espécies com importância biológica. O material híbrido foi preparado pelo processo de inversão de fase e caracterizado pelas técnicas de microscopia eletrônica de varredura acoplada com espectroscopia de energia dispersiva (SEM-EDS) e voltametria cíclica. O composto Azul da Prússia (PB) foi imobilizado na superfície do material por eletropolimerização, aplicando-se um potencial fixo de 20 mV em uma janela de -0,3 V a 1,2 V. Os estudos eletroquímicos do eletrodo modificado CA/G/PB foram realizados em solução de KCl 0,1 mol.L-1, sendo obtidos dois pares redox para a espécie eletroativa imobilizada com potenciais médios (E0) em 0,204 V e 0,842 V, indicando um comportamento quase-reversível. O eletrodo demonstrou alta estabilidade após 500 ciclos redox, não sendo observada lixiviação da espécie eletroativa da superfície da matriz modificada. Os dois pares redox do material híbrido CA/G/PB permaneceram praticamente constantes entre os pH 5,0 e 8,0, indicando que as intensidades de pico não são significativamente afetadas nessa faixa de pH. A correlação linear entre as intensidades de pico e a raiz quadrada da velocidade de varredura, indicou que o sistema possui um comportamento similar aqueles em que o processo é controlado por difusão das espécies eletroativas à superfície do eletrodo. O azul da Prússia imobilizado foi aplicado na determinação de dopamina (DP), ácido úrico (AU), ácido ascórbico (AA) e Paracetamol (PCT) através da técnica de voltametria cíclica, voltametria de pulso diferencial e cronoamperometria. / In this work, we studied the electroanalytical potential of a conductive hybrid material based on cellulose acetate and graphite with electrodeposition Blue conductor film of Prussia (CA / G / PB) as a sensor for species with biological importance. The hybrid material was prepared by phase inversion process and characterized by the techniques of scanning electron microscopy coupled with energy dispersive spectroscopy (SEM-EDS) and cyclic voltammetry. The dye of Prussian blue (PB) was immobilized on the surface of the material by electropolymerization applying a fixed potential of 20 mV in a interval from -0.3 V to 1.2 V. The electrochemical behavior of the modified electrode CA / G / PB were performed in solution of 0.1 mol L-1 KCl being obtained two redox couples for the electroactive species immobilized with midpoint potentials (E0) in 0.204 V and 0.842 V, indicating a quasi-reversible behavior. The electrode showed high stability after 500 redox cycles with no observed leaching of electroactive species to the surface of the modified electrode. The two redox pair of the CA / G / PB electrode was kept practically constant within pH 5.0 and 8.0, indicating that the peak intensities are not significantly affected in this pH range. The linear correlation between peak intensities and the square root of scan rate, indicated that the system has a similar behavior those in which the process is controlled by diffusion of electroactive species to the electrode surface. The immobilized Prussian blue was applied to determine dopamine (DP), uric acid (UA), ascorbic acid (AA) and paracetamol (PCT) by analytical techniques of cyclic voltammetry, differential pulse voltammetry and chronoamperometry.