Made available in DSpace on 2014-06-11T19:35:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-04Bitstream added on 2014-06-13T21:07:13Z : No. of bitstreams: 1 magri_r_dr_araiq.pdf: 2197130 bytes, checksum: a7e11db59a65f29648944760ab420039 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Argilas compreendem uma classe de sistemas micro-heterogêneos complexos e pouco empregados como substratos nos estudos de adsorção. Entretanto, a interação de surfactantes e polímeros com estes substratos em particular, tem sido objeto de averiguações devido a sua importância técnica e industrial. Uma importante propriedade das argilas é a sua capacidade de formar colóides quando dispersas em solução aquosa. Argilas sintéticas são estudadas na presença de surfactantes e polímeros solúveis em água, que em função da interação com a argila em determinada razão argila-polímero-surfactante apresentam propriedades de gel. Em muitos sistemas as argilas orgânicas têm demonstrado remover efetivamente de águas, compostos orgânicos como os hidrocarbonetos aromáticos policíclicos e íons metálicos, os quais são introduzidos no ambiente principalmente pela indústria química e de combustíveis fósseis. No presente trabalho investigou-se a interação de diversos surfactantes e polímeros com a superfície da argila bentonita tendo como objetivo a obtenção de um hidrogel. Os estudos foram realizados em duas etapas. A primeira refere-se ao estudo dos sistemas argila-polímero e argila-surfactante em suspensão buscando encontrar o melhor sistema para a formação do hidrogel e a segunda refere-se ao estudo da interação de diferentes cátions metálicos e compostos orgânicos apolares com o hidrogel. As suspensões, na primeira etapa, foram estudadas por meio da avaliação do comportamento espectrofotométrico do azul de metileno utilizado como molécula sonda, e também por medidas de tensão superficial e de condutividade. Estes estudos permitiram determinar que o melhor sistema para a obtenção do hidrogel é aquele constituído por bentonita e PVA e que a razão entre... / Clays comprise a class of micro-heterogeneous complex and little used as substrates for adsorption. However, the interaction of surfactants and polymers with these substrates in particular, has been the subject of investigations due to its technical and industrial importance. An important property of clay is its ability to form colloids when dispersed in aqueous solution. Synthetic clays are studied in the presence of surfactants and water-soluble polymers, which due to the interaction with the clay in a given reason clay-surfactant-polymer gel have properties. In many systems the organic clays have been shown to effectively remove water, organic compounds such as polycyclic aromatic hydrocarbons and metal ions, which are introduced into the environment mainly by the chemical industry and fossil fuels. In the present study investigated the interaction between surfactants and polymers with the surface of bentonite clay with the objective of obtaining a hydrogel. The studies were conducted in two steps. The first refers to the study of clay-polymer systems and clay-surfactant in the suspension trying to find the best system for the formation of the hydrogel and the second refers to the study of the interaction of different metal ions and polar organic compounds with the hydrogel. The suspensions, the first step has been studied by means of the performance evaluation of the spectrophotometric methylene blue used as a probe molecule, and also measures surface tension and conductivity. These studies determine the best system for obtaining a hydrogel that is composed of bentonite and PVA and the mass ratio of polymer polyvinyl alcohol (PVA) and bentonite clay of 0.25 results in a system fully gelled. In the second stage studies were conducted by the addition of the metal ions... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:35:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-04-19Bitstream added on 2014-06-13T19:05:17Z : No. of bitstreams: 1 ribas_gcb_dr_araiq.pdf: 3555031 bytes, checksum: 870a15eca5c7dcd996e81e1d56ce8831 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os metais nobres Pt, Rh e Ir e suas ligas apresentam diversas aplicações tecnológicas. O Hg pode ser considerado o principal contaminante dos metais nobres e suas ligas binárias e terciárias, por apresentar alta reatividade e uma ação corrosiva sobre os mesmo. Devido a isso, o objetivo deste trabalho foi estudar as reações em estado sólido das ligas Pt-6% Rh e Pt-10% Ir na presença e ausência de Hg, empregando técnicnas eletroquímicas e termogravimétricas. O preparo dos sistemas para os estudos eletroquímicos e de termogravimetria (TG/DTG) constituiu em fazer eletrodeposições de Hg no substrato metálico, com o auxílio de voltametria cíclica, gerando um filme de Hg e compostos intermetálicos sobre a superfície da lâmina. A partir desses resultados, foi possível evidenciar o ataque efetivo do mercúrio sobre o substrato, e a formação de compostos intermetálicos (PtHg, PtHg2, RhHg2 e PtHg4), que foram caracterizados com o auxílio das seguintes técnicas de análise de superfície: microanálise por EDX, mapeamento dos elementos, obtenção de imagens de MEV e difratometria de raios X (XRD). Estas análises de superfície revelaram também, uma distribuição homogênea do Hg, e a presença de um filme de intermetálicos sobre a superfície do substrato. A comparação entre os sistemas Pt-10% Ir-Hg e Pt-6% Rh-Hg sugere uma menor reatividade do substrato de Ir quando são empregadas as mesmas condições experimentais / The noble metals Pt, Rh and Ir and its alloys have many technological applications. Mercury can be considered a major contaminant of noble metals and their binary and tertiary alloys due to high reactivity and a corrosive action on the same. Because of this, the objective was to study the solid state reactions of the alloys Pt-6% Rh and Pt-10% Ir in the presence and absence of mercury, using electrochemical and thermogravimmetry techniques. The preparation of systems for electrochemical and thermogravimmetry (TG/DTG) studies consisted to make electrodepositions of mercury in the metallic substrate, using cyclic voltammetry techniques to generate a film of mercury and intermetallic compounds. From these studies, it was possible to show the actual attack of mercury on the substrate, and the formation of intermetallic compounds (PtHg, PtHg2, RhHg2 and PtHg4), which were characterized using these analysis of surface techniques: EDX microanalysis, mapping of the elements, scanning electronic microscopy and X-ray diffraction (XRD).These analysis also revealed a homogeneous distribution of mercury, and the presence of an film of intermetallic compounds on the surface of the substrate. The comparison between the systems Pt-10% Ir-Hg and Pt-6% Rh-Hg suggesting a lower reactivity of Ir are used when the same experimental conditions

Made available in DSpace on 2014-06-11T19:35:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-05-15Bitstream added on 2014-06-13T21:07:14Z : No. of bitstreams: 1 trindade_mag_dr_araiq.pdf: 2178341 bytes, checksum: ba0619317ab94cb6b7ae6dccb631af90 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho é mostrado o desenvolvimento de diferentes métodos analíticos para quantificação dos corantes Quinizarina (QNZ), Solvente Azul 14 (SB-14), Solvente Azul 35 (SB-35), Solvente Laranja 7 (SO-7) e Solvente Vermelho 24 (SR-24) usados como marcadores em combustíveis. Inicialmente, estudou-se o comportamento voltamétrico dos corantes QNZ e SB-14 sobre eletrodo de carbono vítreo em meio misto de tampão Britton- Robinson/acetonitrila (7:3, v/v) e Britton-Robinson/dimetilformamida (1:1, v/v), respectivamente. Os resultados obtidos mostraram que a oxidação da QNZ ocorre em +0,47 V vs. Ag/AgCl e a redução do corante SB-14 em -0,40 V vs. Ag/AgCl, cujo processo apresenta fortes evidências de um transferência eletrônica reversível, mas complicado por reações químicas acopladas e por adsorção. A voltametria de onda quadrada (VOQ) apresentou desempenho analítico superior às demais técnicas eletroquímicas com limite de detecção da ordem de 4,00×10-7 mol L-1 (QNZ) e 3,00×10-7 mol L-1 (SB-14), além de propiciar um menor tempo de análise. Os métodos eletroanalíticos desenvolvidos acoplados a etapas prévias de extração desses corantes em matrizes como gasolina, querosene e óleo diesel forneceram resultados satisfatórios com valores de eficiência de extração entre 90,0 e 94,0% (QNZ) e entre 87,0 e 98,0% (SB-14), respectivamente. A redução desses corantes também foi monitorada sobre eletrodos de carbono impressos em meio de tampão Britton- Robinson/dimetilformamida (7:3, v/v) visando desenvolver novos métodos de análise. Os resultados foram adaptados ao novo sistema usando surfactante aniônico dioctil sulfosuccinato de sódio (DSS) e catiônico brometo de cetiltrimetilamônio (CTAB) para melhorar a solubilidade dos corantes e aumentar a durabilidade desses eletrodos na presença de solventes orgânicos. Curva analítica no intervalo... / In the present work the development of different analytical methods to quantify the dyes Quinizarine (QNZ), Solvent Blue 14 (SB-14), Solvent Blue 35 (SB-35), Solvent Orange 7 (SO-7) and Solvente Red 24 (SR-24) used as marker in fuels are showed. Firstly, the voltammetric behavior for the dyes QNZ and SB-14 was studied onto glassy carbon electrode surface in a mixture of Britton-Robinson buffer with acetonitrile (7:3, v/v) and in a mixture of Britton-Robinson buffer with N, N-dimethylformamide (1:1, v/v), respectively. The obtained results showed that the oxidation of the QNZ occur at +0.47 V vs. Ag/AgCl and the reduction of the SB-14 occur at -0.40 V vs. Ag/AgCl, which the electrodic process was reversible, but complicated by coupled to chemical reactions and for the adsorption phenomenon. The square-wave voltammetry (SWV) presented analytic performing superior than the other electroanalytical techniques with detection limit around of 4.00×10-7 mol L-1 (QNZ) and 3.00×10-7 mol L-1 (SB-14), besides propitiating a smaller time of analysis. The developed electroanalytical methods coupled with suitable sample pretreatment protocols steps for the extraction of the dyes in fuel samples such as, gasoline, kerosene and diesel oil provide satisfactory results with recovery values between 90.0 and 94.0% (QNZ) and between 87.0 and 98.0% (SB-14), respectively. The reduction of these dyes was also studied onto screenprinted carbon electrode (SPCE) surface in a mixture of Britton-Robinson buffer and N,Ndimethylformamide (7:3, v/v) with the objective to develop new electroanalytical methods. The results were adapted to the new system using anionic Dioctyl sulfosuccinate sodium (DSS) and cationic cetyltrimethylammonium bromide (CTAB) surfactants to improve the dyes solubility and to increase the durability of the electrodes in medium containing organic solvents. Analytical curve in the range... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:35:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-07-20Bitstream added on 2014-06-13T20:06:28Z : No. of bitstreams: 1 lobo_fa_dr_araiq.pdf: 785158 bytes, checksum: d55ebbc7ba58d258c2303cc97a8a276d (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O biodiesel, também conhecido como diesel vegetal, é um combustível obtido de fonte renovável, considerado ambientalmente atraente e uma ótima alternativa em substituição ao diesel. Porém, contaminantes inorgânicos podem estar presentes em amostras de biodiesel devido à absorção de metais pela própria planta (matériaprima) do solo, e/ou podem ser incorporados durante o processo de produção/ transporte/estocagem. Desta forma, por meio de um controle analítico dos teores de contaminantes inorgânicos é possível gerenciar a qualidade dos combustíveis e avaliar o impacto ambiental destes. Este trabalho propõe o desenvolvimento de métodos analíticos para a determinação de Cu, Cd, Ni e Pb em amostras de biodiesel por espectrometria de absorção atômica em forno de grafite (GFAAS). Os procedimentos univariados e multivariados foram aplicados na avaliação das temperaturas ótimas de pirólise e atomização. O planejamento experimental foi usado também como ferramenta para a investigação de dois modificadores químicos (Pd + Mg e W) e dois diferentes procedimentos de preparo das amostras (amostras na forma de microemulsão e amostras digeridas por via úmida em sistema de microondas com radiação focalizada). Considerando que ao usar planejamento fatorial há um melhor entendimento das variáveis e das relações entre elas, os resultados usando o planejamento fatorial foram escolhidos para a determinação dos analitos nas amostras reais de biodiesel. Optou-se por trabalhar com W, pois os as determinações são mais rápidas, há poucos problemas relacionados ao background, durante a deposição do modificador na superfície do atomizador, as impurezas voláteis do modificador podem ser eliminadas, melhorando os limites de detecção, além do W ser um modificador permanente, o que pode aumentar o tempo de vida útil do atomizador. Os procedimentos... / Biodiesel, also known as vegetable diesel, is a fuel obtained from a renewable source and an excellent alternative to diesel. However, biodiesel samples may contain inorganic contaminants due to the plant’s (raw material) absorption of metals in the soil, and/or be incorporated during production, transportation or storage. Therefore, based on the analytical control of the inorganic contaminant content, it is possible to manage the quality of fuels and evaluate their environmental impact. This work proposes the development of analytical methods for the determination of Cu, Cd, Ni and Pb in biodiesel samples using graphite furnace atomic absorption spectrometry (GFAAS). Univariate and multivariate procedures were applied in the evaluation of the optimal temperatures of pyrolysis and atomization. Experimental design was also used as a tool in the investigation of two chemical modifiers (Pd + Mg and W) and two different sample preparation procedures (microemulsions and wet digestion in a focused microwave system). Using a factorial design there is better understanding of variables and relations between them and the results using the factorial design were chosen for the determination of analytes in real samples of biodiesel. Therefore, it was decided to work with W, since the heating programs are faster, there are few background problems, the volatile impurities of the modifier can be eliminated during its deposition on the surface of the atomizer, improving the detection limits, and W is a permanent modifier, which may help prolong the service life of the atomizer. The developed analyticals procedures may also be considered satisfactory as were good values of recovery and low standard deviations for all analytes measured in samples of biodiesel. This work contributes to establish or to propose a suitable normalization, since there is not yet in the literature and / or legislation... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:35:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-10-02Bitstream added on 2014-06-13T20:06:28Z : No. of bitstreams: 1 caldas_nm_dr_araiq.pdf: 765777 bytes, checksum: 6c1192a9a7d34daddd036343b483f969 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Irídio, Ru e W com e sem co-injeção de Pd(NO3)2 + Mg(NO3)2 foram avaliados para a determinação simultânea de As, Cu e Pb em cachaça por espectrometria de absorção atômica em forno de grafite. Irídio com co-injeção de Pd(NO3)2 + Mg(NO3)2, e W com co-injeção de Pd(NO3)2 + Mg(NO3)2, foram selecionados como os melhores modificadores. Para o modificador Ir com co-injeção de Pd(NO3)2 + Mg(NO3)2 curvas analíticas foram construídas em meio de cachaça diluída (1+1, v/v) acidificada a 0,2% (v/v) HNO3 nos intervalos de 0 - 30,0 μg L-1 As, 0 - 1500 μg L-1 Cu e 0 - 60,0 μg L-1 Pb. As massas características foram de 32 pg As, 95 pg Cu e 29 pg Pb, e o tempo de vida útil do tubo foi 520 ciclos de aquecimento. O limite de detecção do método foi de 1,30 μg L-1 As, 140 μg L-1 Cu, e 0,90 μg L-1 Pb. As recuperações das amostras de cachaça enriquecidas variaram de 96% a 106% (As), 92% a 108% (Cu) e 97% a 104% (Pb). O desvio padrão relativo (n=12) foi 4,6%, 13,3%, 8,4% para As, Cu e Pb, respectivamente. Para o modificador W com co-injeção de Pd(NO3)2 + Mg(NO3)2 soluções analíticas para As, Cu, e Pb foram preparadas em 10% (v/v) etanol + 5,0 mg L-1 Ca, Mg, Na, e K acidificados a 0,2% (v/v) HNO3 nos intervalos de concentração de: 0 - 20,0 μg L-1 As e Pb e 0 - 200 μg L-1 Cu. As massas características foram de 16 pg As, 119 pg Cu, e 28 pg Pb e o tempo de vida útil do tudo de grafite foi de aproximadamente 450 ciclos de aquecimento. O limite de detecção do método foi de 0,6 μg L-1 As, 90 μg L-1 Cu e 0,3 μg L-1 Pb. As recuperações das amostras de cachaça enriquecidas com As, Cu e Pb variaram de 94% a 110% (As), 97% a 106% (Cu) e 92% a 108% (Pb). O desvio padrão relativo (n=12) foi 1,0%, 8,3%, 2,7% para As, Cu e Pb, respectivamente. Bismuto e Sb foram utilizados como padrões internos para minimizar efeitos de matriz na determinação direta e simultânea... / Palladium plus magnesium nitrates with and without permanent modifiers (Ir, Ru, W) were evaluated for the simultaneous determination of As, Cu and Pb in cachaça by graphite furnace atomic absorption spectrometry (GF AAS). Iridium coated platform with co-injection of Pd(NO3)2 + Mg(NO3)2 and W coated platform with co-injection of Pd(NO3)2 + Mg(NO3)2 were elected as the optimum surface modification. For Ir-coated platform with co-injection of Pd(NO3)2 + Mg(NO3)2 analytical curves in diluted cachaça (1+1, v/v) containing 0.2% (v/v) HNO3 in the 0 - 30.0 μg L-1, 0 - 1.50 mg L-1 and 0 - 60.0 μg L-1 intervals were obtained for As, Cu and Pb respectively. Characteristic masses were 32 pg As, 95 pg Cu and 29 pg Pb. Lifetime of the tube was around 520 firings. The detection limit was 1.30 μg L-1 As, 140 μg L-1 Cu, and 0.90 μg L-1 Pb. Recoveries of spiked samples varied from 96% to 106% (As), 92% to 108% (Cu) and 97% to 104% (Pb). The relative standard deviations (n=12) were typically 4.6%, 13.3%, 8.4% for As, Cu, and Pb, respectively. For W-coated platform with co-injection of Pd(NO3)2 + Mg(NO3)2, analytical solutions in the 0 - 20.0 μg L-1 As, 0 - 2.00 mg L-1 Cu and 0 - 20.0 μg L-1 Pb were prepared in 10% (v/v) ethanol plus 5.0 mg L-1 Ca, Mg, Na, K and acidified to 0.2% (v/v) HNO3. Characteristic masses were 16 pg As, 119 pg Cu, and 28 pg Pb. The graphite tube lifetime was ca. 450 firings. Limits of detection were 0.6 μg L-1 As, 90 μg L-1 Cu, and 0.3 μg L-1 Pb. Recoveries of the spiked samples varied from 94% to 110% As, 97% to 106% Cu, and 92% to 108% Pb. The relative standard deviations (n=12) were 4,6%, 13,3% and 8,4% for As, Cu, and Pb, respectively. Bismuth and Sb were employed as internal standards (IS) to minimize matrix effects on the direct and simultaneous determination of As, Cu, and Pb using W-coated platform with co-injection... (Complete abstract click electronic access below)

Doctor of Philosophy / Department of Chemistry / Christopher T. Culbertson / In research and industry, almost all chemical analysis methods involve the separation and detection of compounds. Typically, these separations are performed using traditional methods that require volumes in the 10 μL to 10 mL range of sample and in the 200 mL to 2 L range for solvents. These methods are not suitable for low-concentration, volume-limited samples frequently associated with biochemical studies. One way to overcome these limitations is to move the separation and detection to the microscale. The use of the microscale separation technologies enables the study of biological systems that have, until now, been out of reach due to their small volumes or low concentrations. The research presented in this dissertation will discuss two examples of this shift to microscale separation technologies which can solve some small volume sample challenges. These include the detection of protease activity in blood samples for use in cancer detection and the identification of immune system cascade proteins in the mosquito Anopheles gambiae. In Chapter 2 a microfluidic method and device is proposed to monitor protease activities for cancer detection. In this method nanobiosensors are used to measure enzyme activity in biological fluids. These nanobiosensors consist of iron-iron oxide magnetic nanoparticles that are attached to peptide substrates specific for proteases through a disulfide bond. The nanobiosensors are controlled using a neodymium magnet which is attached through a 3D printed adaptor to a rotating motor for mixing and a linear stage to move the nanoparticles between different sections of the device. The separation and detection sections of the device are explained in Chapter 3. Chapter 3 describes the fabrication and optimization of a simple device for microfluidic isoelectric focusing(IEF). IEF is a separation method in which analytes are separated based upon their isoelectric, i.e. neutral charge, points. A reducing agent can be added to the IEF buffer to detach the nanoparticle from the peptide substrate, releasing it for focusing. IEF is also a concentration as well as separation method that will allow the peptide substrates to be focused up to 10⁶ fold. It has a high peak capacity and produces reliable, reproducible separation patterns based on the isoelectric point of the peptide. To meet the detection limits required for cancer detection with proteases, scanning laser induced fluorescence is selected as the method of detection. This scanning system can monitor the separation over time to observe the parameters affecting the separation which cannot be done with typical point or imaging detection systems and allows better separation. This custom automatic detection system can distinguish focused samples of 500 fM from the background with minimal noise from the scanning system. In Chapter 4 the identification of serine protease and inhibitor binding complexes in A. gambiae hemolymph using magnetic bead immunoaffinity chromatography was attempted. These proteases play a key role in the insect innate immunity system and form irreversible complexes. These complexes can be purified from a complex hemolymph sample using an antibody to one of the complex members. To separate the complexes from the hemolymph, Serpin 2 antibodies were attached to protein A coated magnetic beads and then incubated with the hemolymph. Once the purified complexes and Serpin 2 were eluted, the purified proteases were identified on Orbitrap MS. In an attempt to simplify the isolation of the complexes, a magnetic bead mixing rotor column was developed to help reduce the volume of the elution to increase the concentration. This method, however, was not robust and did not improve the concentration.

abstract: Electrophoretic exclusion is a counter-flow gradient focusing method that simultaneously separates and concentrates electrokinetic material at a channel entrance utilizing electric and fluid velocity fields. However, its effectiveness is heavily dependent on the non-uniform field gradients about the entrance. This work assesses the capability of electrophoretic exclusion to capture and enrich small molecules and examines the channel entrance region both quantitatively and qualitatively to better understand the separation dynamics for future design. A flow injection technique is used to experimentally evaluate electrophoretic exclusion of small molecules. Methyl violet, a cationic dye, and visible spectroscopy are used to monitor flow and electrophoretic dynamics at the entrance region resulting in successful capture and simultaneous enrichment of methyl violet at the channel interface. Investigation of the entrance region is performed using both experiment data and finite element analysis modeling to assess regional flow, electric fields, diffusion, convection, and electrophoretic migration. Longitudinal fluid velocity and electric field gradient magnitudes near the channel entrance are quantified using Particle Tracking Velocimetry (PTV) and charged fluorescent microspheres. Lateral studies using rhodamine 123 concentration monitoring agree qualitatively with simulation results indicating decreased gradient uniformity for both electric and fluid velocity fields closer to the channel wall resulting in a localized concentration enhancement at lower applied voltages than previously observed or predicted. Resolution interrogation from both a theoretical assessment and simulation construct demonstrate resolution improvement with decreased channel width and placement of an electrode directly at the interface. Simulation resolution predictions are in general agreement with early experimental assessments, both suggesting species with electrophoretic mobilities as similar as 10-9 m2/(Vs) can be separated with the current design. These studies have helped evolve the understanding of the interface region and set the foundation for further interface developments. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2015

Made available in DSpace on 2014-06-11T19:29:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-06-22Bitstream added on 2014-06-13T19:58:43Z : No. of bitstreams: 1 brugnera_mf_me_araiq.pdf: 4228805 bytes, checksum: 3aeb89396c1f938045e856644dcfa8c2 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / O presente trabalho propõe um método eletroanalítico para determinação dos disruptores endócrinos bisfenol A e nonilfenol em meio micelar utilizando-se eletrodos de carbono vítreo (ECV) e eletrodos de carbono impresso (ECI). Estes disruptores endócrinos têm levantado grande preocupação pois podem promover alterações no sistema endócrino e nível hormonal de humanos, além de sérios efeitos adversos nos organismos aquáticos, mesmo em baixas concentrações. A oxidação do grupo fenólico nos compostos BPA e NP ocorre em potencial 0,42 e 0,56 V, respectivamente em eletrodo de carbono vítreo e em 0,29 e 0,25V para eletrodo de carbono impresso. Curvas voltamétricas obtidas na presença de surfactante brometo de cetiltrimetilamônio (CTAB) têm mostrado maior intensidade de corrente, curvas melhores definidas e minimização dos efeitos de envenenamento da superfície do eletrodo provocado pela adsorção do produto oxidado. Usando-se as melhores condições otimizadas para a determinação de BPA: eletrólito suporte tampão BR pH 8, relação [CTAB]/[BPA] = 2:1 (mol L-1), com os parâmetro de VOQ: f= 60 Hz, Es= 6 mV e Esw= 50 mV e para NP : eletrólito suporte tampão BR pH 11, relação [CTAB]/[NP] = 1:2 (mol L-1), com os parâmetro de VOQ: f= 80 Hz, Es= 6 mV e Esw= 50 mV, construiu-se as curvas analíticas para BPA no intervalo de 1x10-6 a 1x10-5 mol L-1, obtendo-se os limites de detecção e quantificação 7,1x10-7 e 2,4x10-7 mol L-1, respectivamente, em ECV e no intervalo de 3x10-7 a 5x10-6 mol L-1, com LD= 1,1x10-7 mol L-1 e LQ= 3,7x10-7 mol L-1 em ECI. Para NP a curva construida utilizando-se ECV apresentou uma relação linear entre 1x10-9 e 1x10-7 mol L-1, LD= 9,0x10-10 mol L-1 e LQ=2,9x10-9 mol L-1 e em ECI uma relação linear entre 1x10-9 e 4x10-7 mol L-1, LD= 1,0x10-9 mol L-1 e LQ= 3,3x10-9 mol L-1. O método proposto foi aplicado na determinação desses em águas... / This paper proposed an electrochemical method for determination of endocrine disruptors bisphenol A and nonylphenol in micellar media using glassy carbon (GCE) and screen printed electrodes (SPE). This endocrine disruptors can promote changes in the endocrine system and hormone levels in humans, and serious adverse effects on aquatic organisms, even at low concentrations. The oxidation of phenolic group of this compounds BPA and NP occurs in potential at 0.42 and 0.56 V, respectively in ECV and at 0.29 and 0.25 V in SP. The hydrophobic film of CTAB positively charged on the electrode surface promotes both preconcentration of NP and acts as antifouling agent facilitating the removal of its oxidized product that usually passivates the electrode surface. Using the best experimental conditions for BPA: B-R buffer pH8, ratio of [CTAB]/[BPA] = 2:1 (mol L-1), parameters SWV: f= 60 Hz, Es= 6 mV and Esw= 50 mV an for NP: B-R buffer pH 11, ratio of [CTAB]/[NP] = 1:2 (mol L-1), parameters SWV: f= 80 Hz, Es= 6 mV e Esw= 50 mV, the linear calibration graphs were constructed for BPA from 1.0x10-6 to 1.0x10-5 mol L-1 with detection limit of 7.1x10-7 mol L-1 and quantification of 2,4 x10-7 mol L-1 in GCE and from 3.0x10-7 to 5.0x10-6 mol L-1, with LOD= 1.1x10-7 mol L-1 and LOQ= 3.7 x10-7 mol L-1 in SPE. For NP the linear calibration graphs were constructed from 1.0x10-9 to 1.0x10-7 mol L-1, LOD= 9.0x10-10 mol L-1 and LOQ=2.9x10-9 mol L-1 in GCE and from 1.0x10-9 to 4.0x10-7 mol L-1, LOD= 1.0x10-9 mol L-1 and LOQ= 3.3x10-9 mol L-1 in SPE. The electroanalytical method developed was applied for analysis of these compounds in river water and sewage without prior treatment and the results were very satisfactory.A chromatographic method HPLC/DAD was also developed for the determination of BPA and NP. The best conditions were established as mobile-phase acetonitrile/water and flow rate 0.8 mL min-1... (Complete abstract click electronic access below)

Made available in DSpace on 2014-06-11T19:29:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-04-03Bitstream added on 2014-06-13T19:38:06Z : No. of bitstreams: 1 garcia_g_me_araiq.pdf: 720834 bytes, checksum: e19349ecd4bfbb9a08ff4ee78015990a (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Entre os compostos poluentes mais comuns presentes em ambientes abertos e fechados, o ozônio é considerado um dos mais agressivos à saúde humana, e de acordo com estudos realizados pela CETESB sua tendência geral no ambiente tem sido de aumentar sua concentração. Este trabalho descreve o desenvolvimento de novo amostrador passivo para determinação de ozônio troposférico em estudos ambientais. O amostrador passivo construído possui características que possibilitam utilização de menor tempo de amostragem, somente 8 horas. Seu desempenho foi avaliado pela comparação com método ativo, através de amostragens acompanhadas com analisador de ozônio. Os desvios de exatidão e precisão foram respectivamente ± 10,2 % e ± 8,6 %, e os limites de detecção e quantificação foram respectivamente 3,8 ppb e 8,6 ppb. A curva analítica construída apresentou coeficiente angular de 0,88 e coeficiente de correlação (r) de 0,957. O amostrador foi então empregado em estudos de mapeamentos e monitoramentos simultâneos da concentração de ozônio, em escala municipal, com locais de amostragem na cidade de Araraquara, e em escala regional, abrangendo ampla área territorial, com um local de amostragem em cada cidade: Bauru, São José do Rio Preto, Presidente Prudente, Sorocaba e Ribeirão Preto. Após 10 meses de amostragens os resultados comprovaram bom desempenho do amostrador em mapeamentos e monitoramentos simultâneos, identificando locais de pico de concentração do poluente e avaliando o perfil da variação da concentração do poluente ao longo do período do estudo. Este tipo de trabalho pode ajudar a entender melhor o problema e servir como parâmetro importante para auxiliar a CETESB a incluir novos centros de monitoramento, e também a pesquisadores a direcionar suas pesquisas na busca de entendimento mais abrangente do problema inclusive sobre sua ação na saúde da população. / Among the most common pollutants in open and closed environments, ozone is considered one of the most aggressive to human health, according to studies performed by CETESB its general trend in the environment the increasing of its concentration. This paper describes the development of new passive sampler for determination of tropospheric ozone in environmental studies. The passive sampler constructed has features that allow use of small time of sampling, only 8 hours. Its performance was evaluated by comparison with active method, by an ozone analyzer monitoration. The deviations of accuracy and precision were respectively ± 10.2% and ± 8.6%, and the limits of detection and quantification were respectively 3.8 ppb and 8.6 ppb. The analytical curve showed slope constructed of 0.88 and correlation coefficient (r) of 0,957. The sampler was then used in studies of simultaneous mapping and monitoring the concentration of ozone, at municipal level, with sampling locations in the city of Araraquara, and at the regional scale, covering large geographical area with a place of sampling in each city: Bauru , São José do Rio Preto, Presidente Prudente, Ribeirão Preto and Sorocaba. After 10 months the sampling results confirmed the good performance of the sampler in mapping and monitor simultaneously, identifying peak concentration local of the pollutant and evaluating the profile of variation of the concentration of the pollutant over the period of study. This type of work can help better understand the problem and can be an important parameter to help CETESB include new centers for monitoring, and the researchers to direct further studies toward the problem understanding, including its action on the health of population.

Made available in DSpace on 2014-06-11T19:29:07Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-06-23Bitstream added on 2014-06-13T19:17:21Z : No. of bitstreams: 1 silva_lc_me_araiq.pdf: 1267707 bytes, checksum: f59f2d5392cb2f2ac09bc76bc7a49a3f (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Inibidores voláteis de corrosão (IVC) são amplamente utilizados para conferir proteção temporária aos metais ferrosos. Estes inibidores são substâncias que possuem a propriedade de volatilizar a temperatura ambiente, formando uma atmosfera de alta concentração que posteriormente irá se condensar na superfície do metal deixando-o menos suscetível a corrosão. No entanto, estes produtos são comercializados sem que haja padronização e avaliação de qualidade. Atualmente longos ensaios eletroquímicos são utilizados ou somente a quantidade de IVC presente nos suportes é analisada. Pouco estudo tem sido realizado a cerca da quantidade de IVC presente na atmosfera formada. Aminas como monoetanolamina (MEA), monociclohexilamina (MCHA) e diciclohexilamina (DCHA) apresentam propriedades desejáveis de IVC, sendo comumente empregadas. Neste trabalho é desenvolvido um método analítico para avaliar atmosferas modificadas por inibidores voláteis de corrosão. Para coleta e amostragem da atmosfera de interesse otimizouse um método utilizando micro gotas suspensas. Como técnica de separação e determinação utilizou-se a eletroforese capilar (EC) com detecção indireta a 214 nm. Além de eficiente, EC faz uso de micro volumes tornando-a conveniente para o presente estudo. Alternativamente, otimizou-se um método espectrofotométrico a partir da derivação das aminas com o reagente cromóforo p-cloranil, esta técnica foi escolhida visto sua simplicidade e baixo custo. Através dos métodos desenvolvidos foi possível avaliar adequadamente a composição de atmosferas contendo MEA, MCHA e DCHA. Testes colorimétricos em filtros de papel também foram realizados e se mostrou uma alternativa interessante para maiores estudos posteriores. As atmosferas provenientes de amostras plásticas comerciais apresentaram DCHA como principal amina inibidora, apresentando quantidades... / Volatile Corrosion Inhibitors (VCIs) are widely used to provide ferrous metals temporary protection. These substances have the vaporing property at room temperature, making a high concentration atmospheric, which subsequently will condense on the metallic surface, making it less susceptible to corrosion. Therefore, these products are commercialized without proper standardization and quality evaluation. Currently lengthy electrochemical tests are applied or only the amount of VCI on support is analyzed. Little study has been done about the amount of VCI in the atmosphere formed. Amines such as monoethanolamine (MEA), monocyclohexylamine (MCHA) and dicyclohexylamine (DCHA) have desirable properties of VCI and this why are commonly used as one. An analytical method to evaluate modified atmospheres by volatile corrosion inhibitors was developed. Hangdrops were used as collector and sampler of atmosphere, several papers have been published about its versatility and efficiency. Such as separation and determination technique the capillary electrophoresis (CE) with indirect detection to 214 nm was used. In addition other advantage is the use the small volumes by CE. Alternatively, spectrophotometric method was enhanced, amines derivatization by chromophore p-chloranil reagent was used, this technique has been chosen due its simplicity and low cost. By these developed methods is possible to determine rightly the atmosphere composition with MEA, MCHA and DCHA contained. Colorimetric tests were made on filter paper and the results were promising. Results show commercial plastic samples atmosphere have DCHA as the main inhibitor and it was less quantity on support than atmosphere, although DCHA quantities on support after 8 months was kept. Degradation of MEA under salt form was evaluated and results shown beginner solution modification after few days.