Propõe-se método novo e completo para análise de acetona em ar exalado envolvendo coleta com pré-concentração em água, derivatização química e determinação eletroquímica assistida por novo algoritmo de processamento de sinais. Na literatura recente a acetona expirada vem sendo avaliada como biomarcador para monitoramento não invasivo de quadros clínicos como diabetes e insuficiência cardíaca, daí a importância da proposta. Entre as aminas que reagem com acetona para formar iminas eletroativas, estudadas por polarografia em meados do século passado, a glicina apresentou melhor conjunto de características para a definição do método de determinação por voltametria de onda quadrada sem a necessidade de remoção de oxigênio (25 Hz, amplitude de 20 mV, incremento de 5 mV, eletrodo de gota de mercúrio). O meio reacional, composto de glicina (2 mol·L-1) em meio NaOH (1 mol·L-1), serviu também de eletrólito e o pico de redução da imina em -1,57 V vs. Ag|AgCl constituiu o sinal analítico. Para tratamento dos sinais, foi desenvolvido e avaliado um algoritmo inovador baseado em interpolação de linha base por ajuste de curvas de Bézier e ajuste de gaussiana ao pico. Essa combinação permitiu reconhecimento e quantificação de picos relativamente baixos e largos sobre linha com curvatura acentuada e ruído, situação em que métodos convencionais falham e curvas do tipo spline se mostraram menos apropriadas. A implementação do algoritmo (disponível em http://github.com/batistagl/chemapps) foi realizada utilizando programa open source de álgebra matricial integrado diretamente com software de controle do potenciostato. Para demonstrar a generalidade da extensão dos recursos nativos do equipamento mediante integração com programação externa em linguagem Octave (open source), implementou-se a técnica da cronocoulometria tridimensional, com visualização de resultados já tratados em projeções de malha de perspectiva 3D sob qualquer ângulo. A determinação eletroquímica de acetona em fase aquosa, assistida pelo algoritmo baseado em curvas de Bézier, é rápida e automática, tem limite de detecção de 3,5·10-6 mol·L-1 (0,2 mg·L-1) e faixa linear que atende aos requisitos da análise em ar exalado. O acetaldeído, comumente presente em ar exalado, em especial, após consumo de bebidas alcoólicas, dá origem a pico voltamétrico em -1,40 V, contornando interferência que prejudica vários outros métodos publicados na literatura e abrindo possibilidade de determinação simultânea. Resultados obtidos com amostras reais são concordantes com os obtidos por método espectrofotométrico, em uso rotineiro desde o seu aperfeiçoamento na dissertação de mestrado do autor desta tese. Em relação à dissertação, também se otimizou a geometria do dispositivo de coleta, de modo a concentrar a acetona num volume menor de água gelada e prover maior conforto ao paciente. O método completo apresentado, englobando o dispositivo de amostragem aperfeiçoado e o novo e efetivo algoritmo para tratamento automático de sinais voltamétricos, está pronto para ser aplicado. Evolução para um analisador portátil depende de melhorias no limite de detecção e facilidade de obtenção eletrodos sólidos (impressos) com filme de mercúrio, vez que eletrodos de bismuto ou diamante dopado com boro, entre outros, não apresentaram resposta. / A new and complete method for analyzing acetone in exhaled breath is proposed, involving sample collection by preconcentration in water, chemical derivatization and electrochemical determination assisted by a new signal processing algorithm. Breath acetone is under investigation in the medical literature as a biomarker for noninvasive monitoring of clinical conditions such as diabetes and heart failure and better analyzers are demanded. Some amines that react with acetone to form electroactive imines, already studied by polarography in the middle of the last century, were evaluated here as derivatizing agents and glycine presented the best compromise for the definition of a determination method by square wave voltammetry without purging of dissolved oxygen (20 mV pulses at 25 Hz with 5 mV scanning steps, mercury drop electrode). The derivatization medium of glycine (2 mol·L-1) and NaOH (1 mol·L-1) also serves as electrolyte and the imine reduction peak at -1.57 V vs. Ag|AgCl constitutes the analytical signal. For signal processing a novel algorithm based on baseline automatic prediction using Bézier curves was developed in combination with Gaussian peak fitting. This innovative combination enables the recognition and quantification of relatively low and broad peaks on a curved and noisy baseline while standard procedures fail and fitting of splines is less appropriate. The algorithm (available at http://github.com/batistagl/chemapps) was implemented using open source matrix algebra software directly integrated with the potentiostat control software. The generality of this approach to extend the native resources of commercial equipment was evidenced by proceeding the implementation of 3D chronocoulometry with help of the open source Octave language. The processed charge vs. potential vs. time function 3-D surfaces for the forward and backward steps can be observed from any angle on the screen. The fast automatic electrochemical determination of acetone assisted by the Bézier based curve fitting algorithm, with an acetone detection limit of 3.5·10-6 mol·L-1 (0.2 mg·L-1) and a wide linear range is entirely satisfactory for breath analysis. Acetaldehyde, an expected component of breath, especially after ingestion of alcohol, and a common interferent for some other analytical methods, generates a peak at -1.40 V that does not interfere with the acetone determination and that is possibly suitable for simultaneous determination of this analyte. Results obtained with real samples are in agreement with spectrophotometric determinations routinely applied to breath analysis, formerly developed in the master dissertation of the author of this thesis. The geometry of the impinger sampling device was also improved (in comparison with the dissertation) in order to collect the acetone in a smaller volume of cooled water and to allow the patient to breath more freely. The complete method at its current state of development, encompassing the improved sampler and the new effective signal processing algorithm for voltammetric signals is ready for use. Evolution to a portable analyzer can be envisioned if the shortcomings of detection limits of solid (screen-printed) electrode preparation with a mercury film are overcome, once the imine signal was not observed on solid electrodes like bismuth and boron doped diamond.

A insuficiência cardíaca é uma síndrome clínica de alta morbimortalidade e por este motivo é crescente o interesse em se estudar novos biomarcadores da doença visando buscar caminhos para novas estratégias terapêuticas. Neste contexto, a análise do ar exalado pode ser promissora. Baseado nestes dados e na observação de que pacientes com insuficiência cardíaca grave exalam odor peculiar, ainda em estudo piloto, nós identificamos acetona no ar exalado de pacientes com insuficiência cardíaca. Assim, nosso estudo teve por objetivo primário avaliar o papel da acetona exalada como biomarcador do diagnóstico de insuficiência cardíaca e de insuficiência cardíaca descompensada. Como objetivo secundário, avaliar sua relação com a classe funcional segundo a classificação da New York Heart Assocation (NYHA) e sua correlação com o peptídeo natriurético do tipo B (BNP). Entre maio de 2009 e setembro de 2010, pacientes consecutivos com disfunção sistólica (grupo IC) admitidos na emergência (insuficiência cardíaca descompensada grupo ICDESCOMP) e pacientes estáveis nos últimos três meses encaminhados para o teste cardiopulmonar (insuficiência cardíaca compensada grupo ICCOMP) foram submetidos à coleta de ar exalado (extração em água) para posterior análise qualitativa por cromatografia gasosa acoplado à espectrometria de massas e quantificação por espectrofotometria de absorção, através da reação com salicilaldeído. Entre os 235 pacientes avaliados, 89 foram incluídos (59 com insuficiência cardíaca descompensada e 30 com insuficiência cardíaca compensada), 61% do sexo masculino e com mediana de idade de 52 anos. Vinte indivíduos saudáveis (grupo controle) pareados por idade participaram do estudo. O valor mediano (intervalo interquartil) de acetona exalada foi maior no grupo IC em relação ao controle [3,70 g/L (1,69-10,45 g/L) versus 0,39 g/L (0,30-0,79 g/L), p < 0,001]. O valor mediano de acetona em pacientes com insuficiência cardíaca descompensada foi maior do que no grupo com insuficiência cardíaca compensada [7,80 g/L (3,60-15,20 g/L) versus 1,22 g/L (0,682,19 g/L), p < 0,001]. A acurácia do método tanto para o diagnóstico de insuficiência cardíaca (acetona > 1,16 g/L; área sob a curva = 0,94) quanto para o diagnóstico de insuficiência cardíaca descompensada (acetona > 2,50 g/L; área sob a curva = 0,93) foi aproximadamente 85 %, semelhante à acurácia do BNP (BNP > 42 pg/mL; área sob a curva = 0,97 e BNP > 424 pg/mL; área sob a curva = 0,94, respectivamente). Houve correlação positiva entre acetona exalada e BNP (r = 0,772, p < 0,001). Observamos aumento progressivo nas concentrações de acetona exalada de acordo com a piora da classe funcional segundo NYHA (p < 0,001). Assim, podemos concluir que nosso estudo revelou a acetona exalada como um novo biomarcador do diagnóstico de insuficiência cardíaca e de insuficiência cardíaca descompensada, que está associado à maior gravidade da doença e que apresenta correlação positiva com BNP. Sua dosagem é um novo método de diagnóstico não invasivo que pode ser realizado à beira leito, cuja acurácia é semelhante à do BNP / Heart failure (HF) is a condition associated with high mortality and frequent hospital admissions. In this context, multiple biomarkers of heart failure severity have emerged recently. However, the usefulness of most of these biomarkers has not been fully established. Exhaled breath has been considered a suitable tool (biomarker) to evaluate different diseases. Based on the clinical observation that patients with acute decompensated heart failure (ADHF) exhale a distinct odor, in a pilot study we have identified acetone in exhaled breath of heart failure patients and this study aimed to evaluate the role of acetone as a new biomarker of heart failure and ADHF disease. As secondary aims, we intended to analyze the relation to New York Heart Association (NYHA) class and the correlation with B-Type Natriuretic Peptide (BNP). Patients with systolic dysfunction (HF group) admitted consecutively at the emergency room (ADHF group) and stable patients referred to the cardiopulmonary test (chronic HF CHF group) between May 2009 and September 2010 were submitted to exhaled breath collection (extraction into water). Acetone identification was done by gas chromatography-mass spectrometry (GC-MS) and its determination by absorption spectrophotometry after reaction with salicylaldehyde. Twenty healthy subjects matched for age were enrolled (control group). Among 235 patients with HF, 89 were included in the study (59 ADHF and 30 CHF), 61% male, with median age of 52 years. Median exhaled breath acetone value (interquartile range) was higher in the HF group when compared to control group [3.7 g/L (1.69-10.45 g/L) versus 0.39 g/L (0.30-0.79 g/L), p < 0.001] and also higher in ADHF when compared to CHF group [7.80 g/L (3.60-15.20 g/L) versus 1.22 g/L (0.682.19 g/L), p < 0,001]. The accuracy of the method to diagnose CHF (Acetone > 1.16 g/L; AUC = 0.94) and ADHF (Acetone > 2.5 g/L; AUC = 0.93) was similar to the accuracy of BNP (BNP > 42 pg/mL; AUC = 0.97 and BNP > 424 pg/mL; AUC = 0.94, respectively). There was a positive correlation between exhaled breath acetone and plasmatic BNP (r = 0.772, p < 0.001). Levels of exhaled breath acetone were different among the four different NYHA classes (p<0.001). In summary, we can conclude that our study showed exhaled breath acetone as a new biomarker of heart failure and ADHF. It is associated with heart failure severity and has a good correlation with BNP. This is a promising non-invasive diagnostic method of heart failure, whose accuracy is equivalent to BNP

Fuel-air mixing enhancement in axisymmetric jets using an array of synthetic jet actuators around the perimeter of the flows (primarily parallel to the flow axis) was investigated using planar laser-induced fluorescence of acetone. The synthetic jets are a promising new mixing control and enhancement technology with a wide range of capabilities. An image correction scheme that improved on current ones was applied to the images acquired to generate quantitative mixing measurements. Both a single jet and coaxial jets were tested, including different velocity ratios for the coaxial jets. The actuators run at a high frequency (~1.2 kHz), and were tested with all of them on and in other geometric patterns. In addition, amplitude modulation was imposed at a lower frequency (10-100 Hz). The actuators generated small-scale structures in the outer (and inner, for the coaxial jets) mixing layers. These structures significantly enhanced the mixing in the near field (x/D less than 1) of the jets, which would be useful for correcting an off-design condition in a combustor. The amplitude modulation generated large-scale structures that became apparent farther downstream (x/D greater than 1). The impulse at the start of the duty cycle was responsible for creating the structures. The large structures contained broad regions of uniformly mixed fluid, and also entrained fluid significantly. In addition, highly asymmetric forcing geometries displayed the power of the actuators to control the spatial distribution of jet fluid. This spatial control is important for the correction of hot spots in the pattern factor. In order to extend quantitative acetone PLIF to two-phase flows, the remaining unknown photophysical properties of acetone were identified. Tests showed that the technique could simultaneously capture acetone vapor and acetone droplets. A model of droplet fluorescence was developed, and applied to images acquired in a dilute spray. The sensitivity of the model to the value of the unknowns was evaluated, including a best and worst case. The results revealed that several liquid acetone photophysical properties must be measured for the further development of the technique, especially the phosphorescence yield. Quantitative two-phase acetone PLIF will provide a powerful new tool for studying spray flows.

This study combined photocatalytic technology with activated carbon cellulose-paper filter (ACCF) adsorption to decompose gaseous pollutants. Gaseous pollutants were initially adsorbed by activated carbon and could be further decomposed by photocatalytic technology. This study selected acetone (CH3COCH3) as gaseous pollutants. Two market available photocatalysts (photocatalysts¢¹and¢º) were coated on ACCF by impregnation to decompose acetone in a batch photocatlytic reactor. Operating parameters investigated in this study included initial acetone concentration (4.1~10.2 £gM), reaction temperature (40~70¢J), and water vapor (0~20 %). The incident UV light of 365 nm was irradiated by a 20-watt low-pressure mercury lamp placing above the batch photocatalytic reactor. The ACCF coated with TiO2 was placed at the center of the photocatalytic reactor. Acetone was injected into the reactor by a gasket syringe to conduct the photocatalytic tests. Reactants and products were analyzed quantitatively by a gas chromatography with an electron capture detector (GC/DCD) and a flame ionization detector followed by a methaneizer (GC/FID-Methaneizer). Finally, a Langmiur-Hinshewood (L-H) kinetic model was proposed to describe the rate of photocatalytic reaction. Results obtained from the photocatalytic tests indicated that photocatalyst¢º was better than photocatalyst¢¹ for the decomposition of acetone. Experimental results indicated that the size range of self-produced TiO2 photocatalyst by sol-gel was 20~70 nm. The end products were mainly CO and CO2, which resulted in the mineralization ratio up to 98%. Results obtained from the operating parameter tests revealed that the increase of initial acetone concentration enhanced the amount of acetone adsorbed on ACCF, which however did not increase the reaction rate of acetone. Although the increase of reaction temperature could reduce the amount of acetone adsorbed on ACCF, the decomposition rate of acetone could be promoted, so as the yield rate and mineralization ratio of products (CO and CO2). The increase of water vapor could slightly decrease the amount of acetone adsorbed on ACCF. The competitive adsorption phenomenon between acetone and water molecules on active sites could decelerate the decomposion of acetone. Moreover, the ACCF would not be saturated since the adsorbed acetone could be further decomposed quickly by the photocatalysts, which made the TiO2/ACCF more effective on removing acetone and lasted longer than the conventional ACCF. Finally, a modified bimolecular Langmuir-Hinshelwood kinetic model was developed to investigate the influences of initial acetone concentration reaction, temperature, and relative humidity on the promotion and inhibition for the photocatalytic oxidation of acetone. The modified L-H kinetic model could successfully simulate the photocatalytic reaction rate of acetone. Thus, the reaction rate of acetone over TiO2/ACCF could be described by the modified L-H kinetic model.

Made available in DSpace on 2016-12-08T17:19:29Z (GMT). No. of bitstreams: 1 Resumo- marcio.pdf: 103796 bytes, checksum: 51d52d73e2d9ea23ef82572379487b17 (MD5) Previous issue date: 2007-02-26 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The addition of small amounts of carbon nanotubes (CNTs) in polymeric matrices has the potential to origin structural materials with exceptionally high modulus and strength. The extent to which these characteristics will actually be observerd depends on parameters such as degree of purity of the CNT, viscosity of the resin, the cure of the nanocomposites, among others. Aiming to establish an adequate route for the preparation of epoxy nanocomposites, the following aspects have been studied: (i) the effect of acetone addition on the physical and mechanical properties of epoxy; (ii) the CNT reinforcement role in epoxy nanocomposites with different matrix stiffnesses prepared following different curing cycles and (iii) the influence of the CNT content on the nanocomposites. In the first study, solutions with different solvent:epoxy ratio (w/w), namely 0.0, 7.0, 10.0 and 13.0 wt.%, were prepared. It was found that a 10 wt.% acetone addition to the epoxy resin is very beneficial to processes where finely divided fillers, such as carbon nanotubes, are to be incorporated into a resin. Thermogravimetric analysis showed that the cross-linking process of the epoxy was compromised by the presence of residual solvent. Carbon nanotubes (0.25 wt.%) raised the thermal stability of the resin, suggesting a homogeneous dispersion, wich increased its thermal conductivity. The observed increase in Tg indicates that the introduction of nanotubes in the epoxy matrix restricted the movements of the polymeric chains. The viscosity of the epoxy/acetone solution showed a maximum, 12% higher, for a 0.1 wt.% of CNT. Variation in the amount of CNT did not show a significant effect on the thermal stability of the nanocomposites. The DSC, DMA and mechanical test results suggested that the 0.1 wt.% CNT dispersion was more homogeneous than that for 0.25 wt.% SWNT. / A inclusão de baixos teores de nanotubos de carbono (NC) em matrizes poliméricas pode gerar materiais estruturais com excepcionais aumentos no módulo e resistência. Esses fatores dependem de diversos parâmetros como, grau de pureza dos NC, viscosidade da resina utilizada, e cura dos nanocompósitos, entre outros. Visando a obtenção de uma rota adequada para a preparação de nanocompósitos de matriz epóxi, foram estudados: (i) o efeito da acetona no comportamento de cura e nas propriedades de matrizes epóxi; (ii) o efeito de reforçamento de NC em nanocompósitos de matrizes epóxi com diferentes rigidez e (iii) o efeito do teor de NC em nanocompósitos. No estudo (i) foram preparadas amostras com diferentes razões solvente:epóxi (m/m), a saber, 0,0, 7,0, 10,0 e 13,0%. A acetona mostrou-se um solvente adequado para preparação de nanocompósitos de matriz epóxi, bem como para dispersão de nanotubos de carbono. Uma viscosidade mínima foi obtida com o uso de 10% m/m de acetona. Os resultados de análise térmica mostraram que a extensão da reticulação da resina epóxi foi prejudicada pela presença de solvente residual. No estudo (ii) foram preparados nanocompósitos com matriz macia e rígida usando dois ciclos de cura diferentes. O teor de NC usado foi de 0,25% m/m. O aumento moderado observado na Tg foi um indicativo de que a introdução de nanotubos na matriz epóxi restringiu o movimento das cadeias poliméricas. A viscosidade da mistura epóxi/acetona aumentou 12% com 0,1% m/m e voltou a diminuir com 0,25% m/m de NC. O uso de diferentes teores de nanotubos de carbono não teve efeito significativo na estabilidade térmica dos nanocompósitos. Acreditamos de um modo geral, que a dispersão de 0,1% m/m de NC foi mais homogênea que a de 0,25% m/m. Os resultados de DSC e DMA juntamente com os ensaios mecânicos sugerem isso.

Orientador: Maria Alvina Krahenbuhl / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Quimica / Made available in DSpace on 2018-08-08T18:45:17Z (GMT). No. of bitstreams: 1 Silva_LucianaYumiAkisawa_M.pdf: 3646991 bytes, checksum: ba62402781e91d287e8cc031d8f12f30 (MD5) Previous issue date: 2007 / Resumo: No projeto de processos de separação é essencial o conhecimento do comportamento das fases que estão em equilíbrio. O presente trabalho consistiu no estudo do equilíbrio de fases de misturas contendo acetona, água e cumeno. Estes componentes são de grande importância para a indústria do fenol. Os componentes água e cumeno são parcialmente miscíveis e na destilação da mistura de acetona, água e cumeno ocorre a formação de três fases (líquido-líquido-vapor), por isso é muito importante a determinação de um único conjunto de parâmetros dos modelos de GE que possa representar adequadamente o equilíbrio líquido-líquido simultaneamente. Determinou-se dados de equilíbrio líquido-vapor dos sistemas acetona + água,acetona + cumeno e acetona + água+ cumeno e dados de equilíbrio líquido-líquido do sistema água + cumeno a 760 mmHg. O Princípio da Máxima Verossimilhança foi utilizado no ajuste dos parâmetros de interação binária dos modelos NRTL e UNIQUAC.Os parâmetros obtidos neste trabalho foram comparados em trabalho anterior,Mafra (2005,) no qual se procedeu ao ajuste de dados ternários de equilíbrio líquido-líquido a 50 °C, e buscou-se o conjunto de parâmetros que melhor representa o equilíbrio líquido-vapor e líquido-líquido simultaneamente. Os resultados obtidos revelaram que o modelo NRTL com parâmetros determinados a partir de dados binários representa satisfatoriamente os equilíbrios líquido-vapor e líquido-líquido de sistemas binários e ternário envolvendo acetona, água e cumeno / Abstract: On projecting separation processes it is essential the knowledge of the behavior of the phases in equilibrium. The present work involved the study of the phase equilibrium of mixtures containing acetone, water and cumene, which are very important in the phenol industry. The components water and cumene are partially miscible, and in the distillation of the mixture of acetone, water and cumene occurs the simultaneous formation of three phases, two liquids and one vapor. In such a way this it is important the determination of only one set of parameters for GE models that can represent appropriately the vapor-liquid and liquid-liquid equilibrium. It has been determined vapor-liquid equilibrium data of acetone + water, acetone + cumene and acetone + water -"o cumene systems and liquid-liquid equilibrium data of water + cumene system at 760 mmHg. The Maximum Likelihood Principle was used for the estimation of the interaction parameters for the NRTL and UNIQUAC models. The parameters obtained in this work were compared with the parameters found by Mafra (2005). who realized the reduction of ternary liquid-liquid equilibrium data at 50°C. and it has been analyzed which set of parameters gives the best representation of the vapor-liquid and the liquid-liquid equilibrium simultaneously. The results have shown that the NRTL model with parameters determined by binary data represents properly the vapor-liquid and liquid-liquid equilibrium of binary and ternary systems containing acetone, water and cumene / Mestrado / Desenvolvimento de Processos Químicos / Mestre em Engenharia Química

Propõe-se método novo e completo para análise de acetona em ar exalado envolvendo coleta com pré-concentração em água, derivatização química e determinação eletroquímica assistida por novo algoritmo de processamento de sinais. Na literatura recente a acetona expirada vem sendo avaliada como biomarcador para monitoramento não invasivo de quadros clínicos como diabetes e insuficiência cardíaca, daí a importância da proposta. Entre as aminas que reagem com acetona para formar iminas eletroativas, estudadas por polarografia em meados do século passado, a glicina apresentou melhor conjunto de características para a definição do método de determinação por voltametria de onda quadrada sem a necessidade de remoção de oxigênio (25 Hz, amplitude de 20 mV, incremento de 5 mV, eletrodo de gota de mercúrio). O meio reacional, composto de glicina (2 mol·L-1) em meio NaOH (1 mol·L-1), serviu também de eletrólito e o pico de redução da imina em -1,57 V vs. Ag|AgCl constituiu o sinal analítico. Para tratamento dos sinais, foi desenvolvido e avaliado um algoritmo inovador baseado em interpolação de linha base por ajuste de curvas de Bézier e ajuste de gaussiana ao pico. Essa combinação permitiu reconhecimento e quantificação de picos relativamente baixos e largos sobre linha com curvatura acentuada e ruído, situação em que métodos convencionais falham e curvas do tipo spline se mostraram menos apropriadas. A implementação do algoritmo (disponível em http://github.com/batistagl/chemapps) foi realizada utilizando programa open source de álgebra matricial integrado diretamente com software de controle do potenciostato. Para demonstrar a generalidade da extensão dos recursos nativos do equipamento mediante integração com programação externa em linguagem Octave (open source), implementou-se a técnica da cronocoulometria tridimensional, com visualização de resultados já tratados em projeções de malha de perspectiva 3D sob qualquer ângulo. A determinação eletroquímica de acetona em fase aquosa, assistida pelo algoritmo baseado em curvas de Bézier, é rápida e automática, tem limite de detecção de 3,5·10-6 mol·L-1 (0,2 mg·L-1) e faixa linear que atende aos requisitos da análise em ar exalado. O acetaldeído, comumente presente em ar exalado, em especial, após consumo de bebidas alcoólicas, dá origem a pico voltamétrico em -1,40 V, contornando interferência que prejudica vários outros métodos publicados na literatura e abrindo possibilidade de determinação simultânea. Resultados obtidos com amostras reais são concordantes com os obtidos por método espectrofotométrico, em uso rotineiro desde o seu aperfeiçoamento na dissertação de mestrado do autor desta tese. Em relação à dissertação, também se otimizou a geometria do dispositivo de coleta, de modo a concentrar a acetona num volume menor de água gelada e prover maior conforto ao paciente. O método completo apresentado, englobando o dispositivo de amostragem aperfeiçoado e o novo e efetivo algoritmo para tratamento automático de sinais voltamétricos, está pronto para ser aplicado. Evolução para um analisador portátil depende de melhorias no limite de detecção e facilidade de obtenção eletrodos sólidos (impressos) com filme de mercúrio, vez que eletrodos de bismuto ou diamante dopado com boro, entre outros, não apresentaram resposta. / A new and complete method for analyzing acetone in exhaled breath is proposed, involving sample collection by preconcentration in water, chemical derivatization and electrochemical determination assisted by a new signal processing algorithm. Breath acetone is under investigation in the medical literature as a biomarker for noninvasive monitoring of clinical conditions such as diabetes and heart failure and better analyzers are demanded. Some amines that react with acetone to form electroactive imines, already studied by polarography in the middle of the last century, were evaluated here as derivatizing agents and glycine presented the best compromise for the definition of a determination method by square wave voltammetry without purging of dissolved oxygen (20 mV pulses at 25 Hz with 5 mV scanning steps, mercury drop electrode). The derivatization medium of glycine (2 mol·L-1) and NaOH (1 mol·L-1) also serves as electrolyte and the imine reduction peak at -1.57 V vs. Ag|AgCl constitutes the analytical signal. For signal processing a novel algorithm based on baseline automatic prediction using Bézier curves was developed in combination with Gaussian peak fitting. This innovative combination enables the recognition and quantification of relatively low and broad peaks on a curved and noisy baseline while standard procedures fail and fitting of splines is less appropriate. The algorithm (available at http://github.com/batistagl/chemapps) was implemented using open source matrix algebra software directly integrated with the potentiostat control software. The generality of this approach to extend the native resources of commercial equipment was evidenced by proceeding the implementation of 3D chronocoulometry with help of the open source Octave language. The processed charge vs. potential vs. time function 3-D surfaces for the forward and backward steps can be observed from any angle on the screen. The fast automatic electrochemical determination of acetone assisted by the Bézier based curve fitting algorithm, with an acetone detection limit of 3.5·10-6 mol·L-1 (0.2 mg·L-1) and a wide linear range is entirely satisfactory for breath analysis. Acetaldehyde, an expected component of breath, especially after ingestion of alcohol, and a common interferent for some other analytical methods, generates a peak at -1.40 V that does not interfere with the acetone determination and that is possibly suitable for simultaneous determination of this analyte. Results obtained with real samples are in agreement with spectrophotometric determinations routinely applied to breath analysis, formerly developed in the master dissertation of the author of this thesis. The geometry of the impinger sampling device was also improved (in comparison with the dissertation) in order to collect the acetone in a smaller volume of cooled water and to allow the patient to breath more freely. The complete method at its current state of development, encompassing the improved sampler and the new effective signal processing algorithm for voltammetric signals is ready for use. Evolution to a portable analyzer can be envisioned if the shortcomings of detection limits of solid (screen-printed) electrode preparation with a mercury film are overcome, once the imine signal was not observed on solid electrodes like bismuth and boron doped diamond.

It is known that when water is a product in reactions catalysed by cation exchange resins, it inhibits the reaction rate much more than predicted by the reverse reaction or dilution effects. In this work the inhibiting effect is ascribed to the preferential association of the catalytically active sites with water. In the derivation of the kinetic model, a Freundlich type adsorption isotherm was used to quantify the number of sites occupied by water. This is combined with a power law expression for the reaction rate. The resultant expression can accurately predict the reaction rate for various initial concentrations of water and mesityl oxide. Even when water was initially added to the reaction mixture, this model still gave an absolute average error of 6.5% compared to a 54.6% error when the same approach was followed but with the more popular Langmuir isotherm to describe site deactivation. The kinetic expression previously proposed for this reaction system by Klein and Banchero also failed when water was added to the reaction mixture and gave an average error of 71.1%. The procedure used to derive the model is therefore suggested for all cation exchange catalysed reactions where water is one of the products. / Dissertation (MSc)--University of Pretoria, 2005. / Chemical Engineering / unrestricted

Diploma thesis deals with searching of the most appropriate solution of air mass cooling to clear away contained solvents. The solution is based on real and operated pharmaceutical unit. The cooling system is solved as systém of three tubular heat exchangers. In the first heat exchanger the air mass is cooled down by water, in the second by ice-cold water and brine R32 is used for cooling in the third heat exchanger. Heat exchanger system is solved for cooling the air mass which results in condensation of contained solvent – acetone.

In nature, microscopic surface textures impact useful function, such as the drag reduction of shark skin (Dean & Bhushan, 2010) and superhydrophobicity of the lotus leaf(Pan, Kota, Mabry, & Tuteja, 2013). In this study, we explore these phenomena by re-creating microscopic surface textures via the method of interfacial flow instability in drying polyvinylidene fluoride (PVDF) acetone solutions. In general, PVDF films can be made using either spin coating or electrospray deposition with various weight concentrations in acetone. In order to study the morphology of the porous structure of PVDF films, wet deposition samples were fabricated by spin coating or near-field electrospray. Possible theories are discussed and examined to explain the formation of these porous structures resulting in development of a well-controlled method to create porous PVDF films with various pore sizes and pore densities. All samples are characterized and found to exhibit superhydrophobicity and drag reduction. To connect porous PVDF film morphology to the established field of dry particle fabrication, PVDF particle synthesis by far-field electrospray is also reviewed and discussed. An established method to generate polymer particles of different morphologies in other polymers (Almeria-Diez, 2012) by electrospray drying is confirmed using PVDF as well. Due to the ability of scalable and re-configurable electrospray, the microscopic surface textures can be applied to areas of any size to reduce drag or impart water-repelling properties.