Rozprawy doktorskie na temat „Potentiometry”

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
No presente trabalho estudo0se o desempenho eletroquímico de sensores a base de óxido de manganês (IV) do tipo espinélio dopado, para determinação potenciométrica de íons lítio. A matriz porosa de óxido de manganês é formada por unidades de blocos de MnO6 octaédricos que podem formar diferentes estruturas cristalinas. O óxido de manganês tipo espinélio apresenta uma estrutura tridimensional com túneis estruturais próprios e adequados para a inserção do íon lítio. Entretanto, o desempenho eletroquímico desse óxido diminui quando submetido a várias ciclagens de inserção e extração do íon lítio na estrutura do óxido, devido ao efeito de Jahn0Teller (distorção de rede cristalina). Para minimizar o efeito Jahn0Teller, a substituição parcial do íon manganês e do oxigênio por cátions de metais de transição e/ou de ânions, respectivamente, tem sido estudado por vários grupos de pesquisa com objetivo de melhorar o desempenho eletroquímico do óxido na construção de baterias recarregáveis. Dessa forma, foi investigado o comportamento potenciométrico de óxidos de manganês dopados e avaliada sua futura aplicabilidade na determinação do cátion lítio. A resposta potenciométrica para esse cátion é baseada no mecanismo de inserção topotática redox pode ser representada por: 2Mn(IV)O2(s) + 2Li+ (aq) + H2O(l) Li2[Mn2 (III)O4](s) + 2H+ (aq) + ½ O2(g) Os óxidos de manganês dopados estudados foram: Li1,05Ga0,02Mn1,98O3,98; Li1,05Ga0,02Mn1,98S0,02O3,98 e Li1,05Ga0,02Mn1,98F0,02O3,98. Estes óxidos mostraram0se promissores para determinação de íons lítio, pois apresentaram uma maior sensibilidade (80,16, 87,02 e 94,39 mV dec01, respectivamente) quando comparados ao óxido de manganês tipo espinélio não dopado, o qual apresentou uma sensibilidade de 78,9 mV dec01 para pH 8,3. Com relação...
The electrochemical performance of the sensors based on doped spinel0type manganese (IV) oxide for lithium ions potentiometric determination was studied in this work. The porous matrix of manganese oxide is formed by MnO6 0 octahedral structure, which may form different crystal structure. The spinel0type manganese oxide has a three0dimensional structure with own structural tunnels and suitable for the insertion of lithium ion. However, the electrochemical performance this oxide decreases when subjected to various cycles of lithium ions insertion and extraction into oxide structure, ascribed to Jahn0Teller effect (crystal lattice distortion). Thus, to minimize the Jahn0 Teller effect, the partial substitution of manganese and oxygen ions by transition metal cations and/or anions, respectively, has been studied by many research groups with the objective of improving the electrochemical performance of oxide in the construction of rechargeable batteries. Accordingly, the potentiometric behavior of the doped manganese oxide and your application in the lithium cation determination were investigated and evaluated. The potentiometric response for lithium cation was based on topotactic insertion mechanism: 2Mn(IV)O2(s) + 2Li+ (aq) + H2O(l) ↔ Li[Mn2 (III)O4](s) + 2H+ (aq) + ½ O2(g) The doped manganese oxide studied were: Li1,05Mn1,98Ga0,02O3,98; Li1,05Mn1,98Ga0,02S0,02O3,98 e Li1,05Mn1,98Ga0,02F0,02O3,98.. This oxides showed promising application, because presented great sensibility (80.16; 87.02 and 94.39 mV/dec, respectively) when compared to undoped spinel0type manganese oxide, before studied by Teixeira and coauthor, which presented a sensibility of 78.9 mV/dec for pH 8.3. In relation to linear range of response, the result were satisfactory for doped oxide (5.96 x 1005 to 1.62 x1003, 3.49 x 1005 to... (Complete abstract click electronic access below)

The role of magnesium is acknowledged in human physiology even though it is incompletely understood,a nd measuremenot f ionized magnesium by ion-selective electrode analysers is becoming commoner as recent research has alerted clinicians to its importance. Standardisation of ionized magnesium in blood samples in the form of a reference method is required. A prototype reference cell, which was developed for the reference method for ionized calcium, has been tested and found to perform well for magnesium. Selectivity coefficients, and the effects of pH and of proteins on various magnesium selective membranes have been determined. None of these membranes showed sufficient selectivity for magnesium over calcium and sodium for use with serum samples without simultaneous measurement of calcium. Knowledgeo f magnesiums peciationis requiredf or a full understanding of its role in physiology. Stability constants for magnesium and calcium with various ligands have been determined by using a new method in which a pH electrode and a Mg (or, Ca) electrode have been employed simultaneously in alkalimetric titrations. The' results were analysed using the program SUPERQUAD. In general, agreement was very good between values obtained from titrations with Mg (or Ca) electrodes and from pH. The protonation constants of the ligands were also determined and agree well with literaturev alues.R esultsf or Mg-citrate,l actate,g lycinate,a spartatea nd glutamatec omplexationc onstantsc omparew ell with recentlyp ublishedd ata. New systems investigated were Mg-pyroglutamate (Mg-5-oxo-2- pyrrolidinecarboxylic acid) and Mg-pyridoxine (Mg-3-hydroxy-4,5- bis(hydroxymethyl)-2-methylpyridine). Also HEPES (N-(2-hydroxyl) piperazine-N-ethanesulfoniacc id), used in calibration standardsa s a pH buffer, was found not to complex magnesium at physiological pH.

Orientador: Marcos Fernando de Souza Teixeira
Banca: Silvio Rainho Teixeira
Banca: Éder Tadeu Gomes Cavalheiro
Resumo: No presente trabalho estudo0se o desempenho eletroquímico de sensores a base de óxido de manganês (IV) do tipo espinélio dopado, para determinação potenciométrica de íons lítio. A matriz porosa de óxido de manganês é formada por unidades de blocos de MnO6 octaédricos que podem formar diferentes estruturas cristalinas. O óxido de manganês tipo espinélio apresenta uma estrutura tridimensional com túneis estruturais próprios e adequados para a inserção do íon lítio. Entretanto, o desempenho eletroquímico desse óxido diminui quando submetido a várias ciclagens de inserção e extração do íon lítio na estrutura do óxido, devido ao efeito de Jahn0Teller (distorção de rede cristalina). Para minimizar o efeito Jahn0Teller, a substituição parcial do íon manganês e do oxigênio por cátions de metais de transição e/ou de ânions, respectivamente, tem sido estudado por vários grupos de pesquisa com objetivo de melhorar o desempenho eletroquímico do óxido na construção de baterias recarregáveis. Dessa forma, foi investigado o comportamento potenciométrico de óxidos de manganês dopados e avaliada sua futura aplicabilidade na determinação do cátion lítio. A resposta potenciométrica para esse cátion é baseada no mecanismo de inserção topotática redox pode ser representada por: 2Mn(IV)O2(s) + 2Li+ (aq) + H2O(l) Li2[Mn2 (III)O4](s) + 2H+ (aq) + ½ O2(g) Os óxidos de manganês dopados estudados foram: Li1,05Ga0,02Mn1,98O3,98; Li1,05Ga0,02Mn1,98S0,02O3,98 e Li1,05Ga0,02Mn1,98F0,02O3,98. Estes óxidos mostraram0se promissores para determinação de íons lítio, pois apresentaram uma maior sensibilidade (80,16, 87,02 e 94,39 mV dec01, respectivamente) quando comparados ao óxido de manganês tipo espinélio não dopado, o qual apresentou uma sensibilidade de 78,9 mV dec01 para pH 8,3. Com relação... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The electrochemical performance of the sensors based on doped spinel0type manganese (IV) oxide for lithium ions potentiometric determination was studied in this work. The porous matrix of manganese oxide is formed by MnO6 0 octahedral structure, which may form different crystal structure. The spinel0type manganese oxide has a three0dimensional structure with own structural tunnels and suitable for the insertion of lithium ion. However, the electrochemical performance this oxide decreases when subjected to various cycles of lithium ions insertion and extraction into oxide structure, ascribed to Jahn0Teller effect (crystal lattice distortion). Thus, to minimize the Jahn0 Teller effect, the partial substitution of manganese and oxygen ions by transition metal cations and/or anions, respectively, has been studied by many research groups with the objective of improving the electrochemical performance of oxide in the construction of rechargeable batteries. Accordingly, the potentiometric behavior of the doped manganese oxide and your application in the lithium cation determination were investigated and evaluated. The potentiometric response for lithium cation was based on topotactic insertion mechanism: 2Mn(IV)O2(s) + 2Li+ (aq) + H2O(l) ↔ Li[Mn2 (III)O4](s) + 2H+ (aq) + ½ O2(g) The doped manganese oxide studied were: Li1,05Mn1,98Ga0,02O3,98; Li1,05Mn1,98Ga0,02S0,02O3,98 e Li1,05Mn1,98Ga0,02F0,02O3,98.. This oxides showed promising application, because presented great sensibility (80.16; 87.02 and 94.39 mV/dec, respectively) when compared to undoped spinel0type manganese oxide, before studied by Teixeira and coauthor, which presented a sensibility of 78.9 mV/dec for pH 8.3. In relation to linear range of response, the result were satisfactory for doped oxide (5.96 x 1005 to 1.62 x1003, 3.49 x 1005 to... (Complete abstract click electronic access below)
Mestre

In this thesis, we establish the foundations on which graphene based chemical sensors can be developed. Graphene combines several ideal characteristics for potentiometry and charge probing at surfaces which are essential for chemical sensing applications. Hitherto, graphene/substrate interactions have masked the response of graphene based chemical sensors. We demonstrate the use of hydrophobic polymers as a substrate for graphene field effect transistors (FETs) as a means to eliminate undesired graphene/substrate interactions. Parylene gated devices exhibit stable neutrality point gate voltage under ambient conditions, higher mobilities (~10,000 cm2/V.s), and less hysteresis than that observed in graphene FETs with a typical silicon oxide gate. We show quantitatively that electrochemistry involving adsorbed water, graphene, and the substrate is responsible for p-doping in silicon oxide gated graphene FETs. We identify the water/oxygen redox couple as the underlying mechanism for this reaction and capture its kinetics.The aforementioned fundamental studies of graphene permit the development of improved graphene FET based chemical sensors in atmosphere and in solution. We demonstrate that large-area, graphene FETs with a passive parylene substrate and a polyethyleneimine (PEI) functional layer have enhanced sensitivity to CO2 gas exposure. The electron doping of graphene, caused by protonated amine groups within the PEI, is modulated by the formation of negatively charged species generated by CO2 adsorption. The charge doping mechanism is general, and quantitative doping density changes can be determined from the graphene FET characteristics. Finally, we investigate the behavior of graphene FETs in a solution. We present electrochemical techniques to probe the graphene's Fermi level position versus changes in pH. We show that bare graphene devices are not sensitive to changes in pH due to the absence of surface sites available to participate in the protonation and deprotonation process necessary for pH sensing. We finally provide a technique to increase the sensitivity of graphene FETs to changes in pH by utilizing a thin Ta2O5 layer on the graphene surface.
Dans cette thèse, nous établissons les bases selon lesquelles les senseurs chimiques à base de graphène pourront être développés. Le graphène combine plusieurs caractéristiques idéales pour la potentiométrie et la sensibilité aux charges en surface. Ces deux caractéristiques sont essentielles pour des applications de senseurs chimiques. Depuis lors, les interactions entre le graphène et le substrat ont masqués la réponse des senseurs chimiques à base de graphène. Nous démontrons l'utilité de polymères hydrophobe comme substrat pour des transistors à effet de champ (FET) à base de graphène afin d'éliminer les interactions entre le substrat et le graphène. Les dispositifs à base de parylène démontrent une stabilité du point de neutralité dans le voltage de grille, des mobilités supérieures (10000 cm2/Vs) ainsi que moins d'hystérèse que les dispositifs avec une grille à base d'oxyde de silicium. Nous démontrons quantitativement que l'électrochimie entre l'eau adsorbée, le graphène et le substrat est responsable du dopage p dans les FETs à base de graphène et d'oxyde de silicium. Nous identifions le couple redox eau/oxygène comme responsable de cette réaction et nous mesurons la cinétique de cette réaction. Les études fondamentales mentionnées ci-haut permettent le développement de senseurs chimiques à base de graphène dans des conditions ambiantes ainsi qu'en solution. Nous démontrons que des échantillons de large taille de FETs à base de graphène avec une couche de parylène passivé et une couche fonctionnelle de polyethyleninine (PEI) augmentent la sensibilité au CO2. Le dopage aux électrons du graphène, causé par la protonation des groupes aminés dans le PEI, est modulé par la formation d'espèces chargées négativement par l'absorption de CO2. Le mécanisme de dopage de charge est général et la densité du dopage peut être déterminée par les caractéristiques des FETs à base de graphène.Finalement, nous investiguons le comportement des FETs à base de graphène en solution. Nous présentons des techniques électrochimiques afin de mesurer la position du niveau de Fermi dans le graphène en fonction de changement du pH. Nous démontrons que des dispositifs sans PEI ne sont pas sensibles aux changements de pH à cause de l'absence de sites en surface capables de participer à la protonation et la dé-protonation nécessaire pour être sensible au pH. Nous présentons finalement une technique pour augmenter la sensitivité des FETs de graphène aux changements de pH en utilisant une fine couche de Ta2O5 sur la surface du graphène.

The specificity of biosensors is achieved by the use of biological probes with affinity to the targets to be detected. The electrochemical transducer converts the biological recognition process into an electrical signal. The resulting electrical signal is the response of the recognition from the biolayer. Potentiometric, amperometric and voltammetric detection are the fundamental electrochemical measurement techniques. In this thesis, direct open circuit potentiometry (OCP) is studied with several types of electrochemical systems. The biological interaction between the probes and the targets are characterised by measuring the variations of the true open circuit potential (OCP) that occurs at the surface of the working electrode when the charge density and the distribution of the immobilised biolayer change upon interactions with the target biomolecules. OCP is a detection technique which measures the recognition electrical signal in real time. With the true OCP measurement system developed in-house, a number of electrochemical systems were studied by looking at the interaction with different biomolecules, to show that a true OCP measurement system could be achieved for biosensor development. The electrochemical systems that have been investigated include DNA – DNA detection with a novel cobalt complex for signal enhancement, PNA – DNA detection with gold nanoparticles for signal enhancement, and protein phosphorylation (for drug discovery applications) with gold nanoparticles for signal enhancement. A comparison with promising biosensing techniques such as electrochemical impedance spectroscopy (EIS) and other techniques is performed to demonstrate the benefits of OCP as a biosensing technique. An easily expandable multichannel OCP biosensor array instrumentation system was developed. The whole instrumentation is built and assembled with a custom designed electronic system, a microfluidic system and its applicability demonstrated for a range of electrochemical systems. Through an investigation of the instrumentation amplifier circuit and the multiplexing technique, and the analysis of experimental data, an optimisation for the OCP measurement system is achieved. This thesis tackles a gap in the literature in terms of studies of OCP as a biosensing technique, providing a number of case studies that can contribute towards the development of potential new low-cost biosensors.

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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

This thesis describes the development and application of stripping potentiometric methods for reliable determination of some trace metals in natural waters on a glassy carbon mercury film electrode (GCMFE). The development of these methods involved investigation of factors influencing the stripping potentiometric measurement, such as selection of adequate supporting electrolyte, choice of pH and/or concentration of supporting electrolyte, oxidant concentration, deposition potential, deposition time, stirring or sample rotation rate and equilibrium period. Moreover, the influence of complexing agents and the magnitude of constant current were carefully investigated for adsorptive cathodic stripping potentiometric methods. In addition, linear concentration range and detection limits were considered. The analytical application of the method to some natural waters was also demonstrated. It is concluded that the stripping potentiometric methods developed in this study are adequate for ultra-trace determination of copper, lead, cadmium, zinc, nickel and molybdenum. The methods provide very simple procedures, excellent precision and accuracy for the reliable determination of the six metals in natural water samples.

Two objectives are achieved in this thesis: (1) to develop a new method to measure the pH-dependent net surface charge of soils and (2) to determine if, by a combination of the surface charge evaluated by potentiometric titration and ion adsorption, we can separate the permanent charge, generated by the isomorphous substitution, from the variable charge. First, a laboratory procedure, using backtitration, was developed for the measurement of the pH-dependent net surface charge. This method was tested on ten soil horizons from Gleysols and Podzols. It appears that the pH-dependent net surface charge, measured by this technique, shows good agreement with that measured by ion adsorption. It is also possible, with this method, to identify some plateaus and inflection points in the backtitration curve associated with protonation/deprotonation reactions of specific soil components. Secondly, it was demonstrated that it is possible to increase the surface charge of montmorillonite with Al-oxide coatings under specific conditions.

No presente trabalho comprova-se o efeito prejudicial do oxalato, utilizado para a separação prévia de cálcio e magnésio, na determinação complexométrica deste último com EDTA em águas, usando-se em titulação visual o indicador Negro de Eriocromo T e, em titulação potenciométrica, o sistema indicador Hg/Hg-EDTA. Comprovou-se, também, a viabilidade de se usar como titulante uma solução de EDTA \"tetraneutralizado\", em titulações potenciométricas com medidas de pH através de eletrodo de vidro combinado. Neste caso o ponto final é obtido através da hidrólise da espécie Y4-, após o ponto de equivalência. Assim evidenciou-se a viabilidade de um novo método para a determinação da mistura de cálcio e magnésio, pelo uso EDTA \"tetraneutralizado\" e separação prévia dos dois cátions através da adição de oxalato. A detecção do ponto final nestas titulações com EDTA \"tetraneutralizado\" pode também ser feita visualmente com fenolftaleína. O efeito de volume em titulações potenciométricas em geral, num certo nível de concentração, foi objeto de análises diversas inclusive por cálculo computacional de curvas derivativas. Comprovou-se que quanto menor o volume do titulado maior é o salto potenciométrico obtido, caracterizando-se o que se denominou de \"paradoxo potenciométrico\", pois uma menor massa de substância pode ser titulada com, teoricamente, o mesmo erro relativo que para uma massa maior de substância.
Alternative method for the complexometric determination of magnesium. Influence of volume on potentiometric titrations. Keywords: Potentiometry, Magnesium, EDTA. Present paper has been found the negative effect of oxalate, used to the previous separation of calcium and magnesium in a complexometric determination of this last with EDTA in waters, using at visual titration Eriochrome black T as indicator and at potentiometric titration the indicator system Hg/Hg-EDTA. It has been found, also, the viability in the use as titrant a \"tetraneutralized\" EDTA solution, in potentiometric titration with measurements of pH with the glass electrode. In this case the end point is obtained on basis of hydrolysis of Y4- species, after the equivalent point. So it has been displayed the viability of a new method to the determination of the mixture calcium and magnesium by the use of \"tetraneutralized\" EDTA and previous separation of both cations by addition of oxalate. The end point detection can be visually found, in these titrations with \"tetraneutralized\" EDTA, by using of phenolphthalein. The effect of volume in potentiometric titration in general, at a defined concentration level, was subject of several analysis incluse using the compute calculation of derivative curves. It has been found that as smaller volume of titrated performes a higher potentiometric jump, this effect was called for us \"potentiometric paradox\", since an smaller weight of substance can be titrated, with theoretically, the same relative error that to a greater weight of substance.

Разработана методика определения степени дехлорирования пестицидов в почве и воде. Она заключается в том, что после инкубирования образцов с пестицидом сравнивают содержание хлор-ионов в опыте и контроле. При цитировании документа, используйте ссылку http://essuir.sumdu.edu.ua/handle/123456789/19010

Thesis (MTech (Chemistry))--Cape Peninsula University of Technology, 2016.
Boron concentration analysis is an important and critical analysis performed by the Analytical Chemistry Laboratory at Koeberg Nuclear Power Station (KNPS), because boron controls reactivity and the concentration determination is a Technical Specification Parameter (safety parameter). Hence accurate, precise results for boron concentration produced by laboratories and on-line analysers are important because of their operational implications associated with reactivity control and also for nuclear safety. The project focused on comparing the quality of chemical analysis results of boron produced by analysis techniques/ methods used at Koeberg Nuclear Power Station namely; Potentiometric Titration, Atomic Absorption Spectrophotometry (Flame) and UV-VIS Azomethine-H method. The methods were described, optimised, evaluated and compared in terms of uncertainty of measurement, accuracy, precision, analysis range, limitations, appropriateness and applicability for boron analysis in 2500 mg B/kg concentration range. For Potentiometric Titration method, the measurement uncertainty = 2500 ±16 mg B/kg, accuracy= 0.2%, precision= 0.08% the range of analysis= 5-800 mg B/kg. For Atomic Absorption Spectrophotometry (Flame) the measurement uncertainty= 2500 ±51 mg B/kg, accuracy= 0.12%, precision= 0.44% the range of analysis= 0 -500 mg B/kg. For UV-VIS Azomethine-H the measurement uncertainty= 2500 ±72 mg B/kg, accuracy= 0.08%, precision= 0.44% the range of analysis= 0 -10 mg B/kg. The INPOs 95% accuracy and precision criteria for boron is ± 1%. So these techniques could be used for boron analysis in PWR. Based on the evaluation and assessments mentioned above; the Potentiometric Titration was found to be the most preferred method for boron analysis for Pressurised Water Reactors followed by Atomic Absorption Spectrophotometry (Flame) that can be of good use in determining boron especially in waste samples and samples with complex matrices. The UV-VIS Azomethine-H methods can only be used when it is really necessary to determine very low levels of boron between 0- 10mg B/kg of which it was never required before. Since it is specifically the B-10 isotope that is responsible for the ability to control reactivity, the implementation of isotopic boron analysis (by Inductively Coupled Plasma – Mass Spectrometry) at KNPS is explained and the advantage of the programme is illustrated. Although the current state of instrumental capabilities is adequate for 10B isotope determination, further work of optimising the methodology for even better results is recommended.

O presente estudo procura dar continuidade a um dos ramos de pesquisa desenvolvidos na área de Analítica do Instituto de Química da USP, onde se procura estudar a química de complexos formados entre diferentes metais e o ânion azoteto, N-3. O cátion índio(III), à semelhança do que ocorre com o ferro (III), complexa com o ânion azoteto em meio aquoso. Este poder de complexação foi constatado em estudos polarográficos do sistema In N3+ / N-3 ora em desenvolvimento. A obtenção das constantes de estabilidade dos complexos formados entre o In3+ e o ligante azoteto, por via potenciométrica, baseia-se na alteração do pH do tampão formado por N-3 e o ácido fraco HN3, quando se adicionam íons In3+. O acompanhamento da variação da concentração hidrogeniônica foi f.eito com o auxílio do eletrodo de vidro combinado. A concentração de N-3 de equilíbrio variou de valores próximos de zero a 90 mM, para que se obtivessem dados na mais larga faixa de concentraç6es de ligante. Manteve-se a força iônica das soluções em 2,00OM (NaCI04) e trabalhou-se a 25,0οC. A análise dos dados experimentais e tratamento matemático dos mesmos, evidenciaram a formação de complexos mononucleares e os valores das constantes globais encontrados foram: β1 = (2,0 ± 0,1) x 103M-1 β2 = (7 ± 3) x 105M-2 β3 = (5 ± 1) x 107M-3 β4 = (7 ± 3) x 108M-4
The present study is a branch of the main work concerned with the complex formation between several metal cations and azide anion in aqueous media. Indium (III) was selected, in analogy to iron (III), because forms complexes with azide in aqueous media. Polarographic studies in development showed the tendency of these complexation. To determine the stability constants of complexes was used potentiometric method using glass e1ectrode. The main advantage is based on pH modification of the buffer solution constituted by azide and hidrazoic acid (N-3;/HN3) when indium (III) cations are added in the buffer. The azide concentration was a1tered from near zero to 90 mM, the ionic strenght he1d at 2,000 M with sodium perchlorate and the temperature kept constant at 25,0°C. The evaluation of experimental data shawed mononuclear species and the global constants found were: β1 = (2,0 ± 0,1) x 103M-1 β2 = (7 ± 3) x 105M-2 β3 = (5 ± 1) x 107M-3 β4 = (7 ± 3) x 108M-4

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In this paper, we propose the determination of lansoprazole content, selective inhibitor of H + / K + -ATPase gastric using titration based on digital image (Digital Image-Based Titration). The DIB system uses a webcam to acquisition of digital images based on the color system RGB (Red-Green-Blue). During the titration procedure the method was applied to the acid-base titration of the drug lansoprazole with hydrochloric acid. The titration was performed by the DIB, and by potentiometry. In DIB methodology for each volume of titrant added an image was captured and manipulated to obtaining the standard values (N=√R̅2+G̅2+B̅2). The spent volume of titrant to reach the equivalence point was obtained from the second derivative of the titration curve. The results of the samples showed no statistically significant differences at the 95% confidence level was observed after applying the paired t test (tcalculado = 0,439 e tcrítico = 2,353). The relative standard deviations using the DIB methodology with the exception of Sample C, was below 1.0%.
Neste trabalho, propõe-se a determinação do teor de lansoprazol, agente inibidor seletivo da H+/K+-ATPase gástrica, utilizando titulação baseada em imagem digital (Digital Image-Based Titration). O sistema DIB utiliza uma webcam para aquisição das imagens digitais com base no sistema de cor RGB (Red-Green-Blue). Durante o procedimento de titulação o método foi aplicado na titulação ácido-base do fármaco lansoprazol com o ácido clorídrico. A titulação foi realizada por DIB e por potenciometria. Na metodologia DIB para cada volume do titulante adicionado uma imagem era capturada e manipulada para obtenção dos valores da norma (N=√R̅2+G̅2+B̅2). O volume gasto de titulante para atingir o ponto de equivalência, foi obtido a partir da segunda derivada da curva de titulação. Os resultados obtidos das amostras não apresentaram nenhuma diferença estatística significativa no nível de confiança de 95 % que foi verificada após aplicar o teste t emparelhado (tcalculado = 0,439 e tcrítico = 2,353). Os desvios padrão relativos utilizando a metodologia DIB, com exceção da amostra C, ficaram abaixo de 1,0 %.

The aim of this thesis is the development of solid contact ion selective electrodes, ISEs, where the transducer layer is made of a network of carbon nanotubes.

Potentiometric classical ion selective electrodes (ISEs) have been used for analytical applications since the beginning of 1900's. Determination of pH by a glass membrane ion selective electrode emerged at the beginning, being the first ISEs developed. pH glass electrode is still one the most useful and robust sensors for routine measurements both in laboratories and industries.

Throughout the years, new technologies, ideas and designs have been developed and incorporated successfully in the potentiometric fields so as to provide answers to the new society's needs. Therefore, the ion selective electrodes developed in this thesis are a step further in the progress of ISEs and must be considered as products of the scientific envisioning, growth, and interdisciplinary cooperation of many research teams over many years of continuous efforts.

The sensing part can be regarded nowadays as well developed, although it has been during only the last few years when considerable improvements have taken place in the development of new polymeric membranes, ionophores and lipophilic ions. Moreover, the understanding of the theoretical sensing mechanism has been a powerful solid backbone in the rise of ISEs.

Miniaturization of classical ISEs requires making all solid contact electrodes to avoid the intrinsic drawbacks of the inner solution. In this manner, the transduction layer has been the focus of attention for the two last decades. New solid contact transducers having the capacity to convert an ionic current into an electronic current have been emerging. Within them, conducting polymers have played an important role in the transduction of the potentiometric signal, being the most used in solid contact ion selective electrodes (SC-ISEs) up to now. However, the behaviour of conducting polymers can be further improved. For instance, their sensitivity to light one of main operational issues yet to be solved.

In the present context of searching for new materials able to transduce potentiometric signals we selected and tested carbon nanotubes (CNTs). CNTs, which were rediscovered by Ijima in 1991, display excellent electronic properties in terms of signal transduction. In addition, due to their chemical reactivity CNTs can be easily functionalized with receptors or other functional groups. In fact, depending on the type of functionalization the macroscopic and microscopic properties of CNTs can be drastically changed. This nanostructured material had not been used previously as a solid contact material in ISEs.

The main aim of this thesis is to demonstrate that CNTs can act as a clean and efficient transducer in SC-ISEs overcoming the drawbacks displayed by the previously assayed solid contact materials. The developed electrodes were used in different conditions to determine several ions in different sample types, demonstrating the capabilities of this nanostructured material.
The thesis has been structured in different chapters, each one containing the following information:

· Chapter 1 provides a short historical overview of potentiometric ISEs. The evolution from the "classical ISEs" to the SC-ISEs is briefly illustrated. Once the motivation for thesis is described, the general and specific objectives of the thesis are reported.
· Chapter 2 reports the scientific foundations of the developed electrodes. All components of the ISE, sensing layer, transducers and detection systems are introduced. Analytical performance characteristics of ISEs are also described.
· Chapter 3 corresponds to the experimental part. Reagents, protocols, procedures and instruments used in the thesis are reported.
· Chapter 4 provides the demonstration that CNTs can act as a transducer layer in SC-ISEs. The first SC-ISEs based on CNTs are characterized by electrochemical and optical techniques.
· Chapter 5 contains the experimental results that lead to the elucidation of the possible transduction mechanism of CNTs in SC-ISEs. Electrochemical impedance spectroscopy (EIS) is employed as the main characterization technique.
· Chapter 6 is composed of four sections reporting different analytical applications. In the first section, the common pH electrode is developed using a solid contact technology based on CNTs. In the second section, the development of SC-ISEs based on a new synthetic ionophore selective to choline, and CNTs as transducers is shown. In the third section, watertight and pressure-resistant SC-ISEs based on CNTs are developed and tested in aquatic research to obtain information about the gradient profiles along the depth of the lakes. In the fourth section, SC-ISEs based on CNTs are adapted for the on-line control of a denitrification catalytic process.
· Chapter 7 reports the possibilities of miniaturization of the SC-ISEs based on CNTs to reach a nanometric electrode. Potentiometric and optical characterizations are described in this section. Moreover, a discussion about the limitations of the real miniaturization in potentiometry is undertaken.
· Chapter 8 points out the conclusions of the thesis. In addition, future prospects are suggested.
· Finally, several appendices are added to complete the doctoral thesis.
El principal objetivo de esta tesis es el desarrollo de electrodos selectivos de iones de contacto sólido, ESIs-CS, utilizando como capa transductora una red compuesta de nanotubos de carbono.

Los electrodos potenciométricos selectivos de iones han sido utilizados en aplicaciones analíticas desde comienzos de 1900. La determinación de pH mediante electrodos de vidrio selectivo de iones fue el primer ESI desarrollado. Hoy en día, el electrodo de vidrio para la determinación de pH es todavía uno de los más útiles y robustos sensores utilizados en mediciones rutinarias tanto en laboratorios como en industrias.

A lo largo de los años, nuevas tecnologías, ideas y diseños han sido desarrollados e incorporados satisfactoriamente en el campo potenciométrico proporcionando soluciones a las necesidades en continua evolución de la sociedad. De esta manera, los electrodos selectivos de iones desarrollados en esta tesis son un paso más en el progreso de los ESIs y deben ser considerados como el producto de una sólida base científica, del crecimiento y de la cooperación interdisciplinaria de diversos grupos de investigación durante varios años.

La parte del sensor donde tiene lugar el reconocimiento químico y donde se genera el potencial dependiente de la muestra en estudio en los ESIs se puede considerar, en estos días, ampliamente desarrollada, aunque considerables mejoras han tenido lugar durante los últimos años, especialmente en el desarrollo de nuevas membranas poliméricas, ionóforos e iones lipofílicos. Sobretodo, el estudio y la comprensión del mecanismo teórico del sensor ha sido muy importante en el crecimiento y desarrollo de los ESIs.

El concepto de electrodos selectivos de iones de estado sólido surge como requisito vital para evitar las intrínsecas desventajas de la solución interna, en el proceso de miniaturización de los ESIs clásicos. De esta forma, la capa transductora ha sido el principal punto de atención durante dos décadas. Así, nuevos transductores de contacto sólido con la capacidad de convertir una corriente iónica en una corriente electrónica han sido desarrollados. Entre ellos, los polímeros conductores han jugado un importante papel en la transducción de la señal potenciométrica, siendo éstos los más empleados en los electrodos selectivos de iones de contacto sólido (ESIs-CS). Sin embargo el comportamiento de los polímeros conductores puede ser mejorado. Por ejemplo, la sensibilidad hacia la luz de estos materiales es un inconveniente todavía no resuelto.

En este contexto de investigación de nuevos materiales capaces de actuar como transductor de una señal potenciométrica, se han escogido y estudiado los nanotubos de carbono (NTCs) como transductores. Los NTCs fueros redescubiertos por Ijima en 1991, y muestran excelentes propiedades electrónicas en términos de traducción de señal. Además, debido a su reactividad química, los NTCs pueden ser fácilmente funcionalizados con receptores u otros grupos funcionales. De hecho, sus propiedades macroscópicas y microscópicas pueden ser afectadas drásticamente dependiendo del tipo y grado de funcionalización. Este material nanoestructurado no había sido previamente utilizado como transductor en ISEs.

El principal propósito de esta tesis es demostrar que los nanotubos de carbono pueden actuar de forma eficiente como transductor en electrodos selectivos de iones de estado sólido logrando vencer las desventajas de los transductores previamente mencionados. Los electrodos desarrollados fueron usados en diferentes condiciones para determinar distintos iones en diversos tipos de sistemas, demostrando las extraordinarias capacidades de este material nanoestructurado.


Esta tesis ha sido estructurada en capítulos que contienen la siguiente información:

· El Capítulo 1 proporciona una breve visión histórica de lo electrodos potenciométricos selectivos de iones. Se ilustra la evolución desde los "clásicos ESIs" hasta los actuales "ESIs-CS". Además se señalan en esta sección los objetivos generales y específicos.
· El Capitulo 2 contiene las bases científicas de los electrodos desarrollados. Se introducen todos los componentes que integran un ESI, tales como: capa reconocedora, capa transductora y sistema de detección. A continuación se describen los parámetros analíticos de calidad de los ESIs.

· El Capitulo 3 describe la parte experimental. Se recogen los reactivos, protocolos, procedimientos e instrumentos usados a lo largo de la tesis.
· El Capitulo 4 provee de la demostración de que los NTCs pueden actuar eficientemente como capa transductora en SC-ISEs. Se caracteriza el primer ESI-CS integrado por NTCs mediante técnicas ópticas y electroquímicas.
· El Capitulo 5 contiene los resultados experimentales que permiten la posible elucidación del mecanismo de transducción de los NTCs en los ESIs-CS. La Espectroscopia de Impedancia Electroquímica (ESI) es utilizada como la principal técnica de caracterización.
· El Capitulo 6 está integrado por cuatro secciones con diferentes aplicaciones analíticas. En la primera sección, se desarrolla un electrodo de pH que usa NTCs como nueva tecnología transductora en ESIs-CS. En la segunda sección se muestra el desarrollo de un ESI-CS integrado por un ionóforo sintético selectivo a colina, y NTCs como transductores. En la tercera sección, ESIs-CS basados en NTCs, resistentes a altas presiones y totalmente herméticos, se desarrollan y prueban en investigaciones acuáticas con la finalidad de obtener información sobre los gradientes de concentración de iones en función de la profundidad de un lago. En la cuarta sección ESIs-CS basados en NTCs se adaptan para el control on-line de un proceso catalítico de desnitrificación.
· El Capitulo 7 presenta la posibilidad de la miniaturización de los ESIs-CS basados en NTCs logrando obtener un electrodo nanométrico. Se muestran en esta sección la caracterización óptica y potentiométrica. Además, se discuten las limitaciones de la miniaturización real de los ESIs en potenciometría.
· El Capitulo 8 contiene las conclusiones de la tesis. Adicionalmente, se sugieren las perspectivas futuras del trabajo presentado.
· Finalmente, se añaden algunos apéndices como complemento de la tesis doctoral.

Blodgassprutor beställs för att undersöka en patients syra-bas-status, laktatkoncentration och elektrolytkoncentration. Några orsaker till balansrubbningar kan vara trauma, syrebrist, infektion, intoxikation eller svält. År 2018 installerades ett nytt rörtransportsystem på Västerviks sjukhus och syftet med studien var att undersöka om det är möjligt att transportera blodgassprutor i det nya rörsystemet utan att provresultat påverkas. Analyser som studerades var pH (power of hydrogen), syretryck, koldioxidtryck, syrgasmättnad, natriumjoner, kaliumjoner, fria kalciumjoner, standardbikarbonat, basöverskott och laktat. Studien omfattade 27 arteriella dubbelprover där det ena provet transporterades i rörtransportsystemet och det andra transporterades manuellt till laboratoriet. Proverna analyserades på instrumentet ABL 800 Flex, inom 30 minuter efter provtagning, med analysmetoderna potentiometri, amperometri och spektrofotometri. Resultaten jämfördes i korrelationsdiagram med en regressionslinje för att påvisa samband mellan proverna. Korrelationsdiagrammen visade positiv linjär korrelation hos samtliga analyser och ett samband kunde påvisas (r = 0,930-0,998). Om resultatet från proverna som transporterats manuellt ökade, ökade även resultatet från proverna som transporterats i rörpost och tvärtom. Ett stapeldiagram skapades för att visualisera skillnader i medelvärde som visade en liten skillnad på basöverskott som ökade efter transport i rörpostsystemet. Ett tvåsidigt parat t-test utfördes för att påvisa om någon signifikant skillnad förelåg mellan analysresultaten. T-testet visade en statistisk signifikant skillnad på syretrycket (p = 0,04), syrgasmättnaden (p = 0,04), basöverskott (p = 0,001) och standardbikarbonat (p = 0,006), då medelvärdet ökade efter transport i rörpost. Medelvärdet för halten natriumjoner minskade efter transport i rörpostsystemet vilket innebar att hemolys inte förekom. Slutsatsen var att det finns en signifikant skillnad mellan blodgassprutor transporterade i rörpostsystem och blodgassprutor transporterade manuellt på vissa analyser, men skillnaden har ingen klinisk betydelse.
Blood gas syringe are ordered to examine the patient´s acid-base status, lactate concentration and electrolyte concentration. Some causes for imbalance could be trauma, lack of oxygen, infection, poisoning or starvation. In 2018, a new pneumatic tube transport system was installed at Västervik´s hostpital and the purpose of this study was to investigate if it is possible to transport samples for blood gas analyses with the new pneumatic tube transport system without affecting the test results. The analyses which were investigated were pH (power of hydrogen), oxygen tension, carbon dioxide tension, saturation, sodium ions, potassium ions, free calcium ions, standard bicarbonate, base excess and lactate. The study included 27 arterial double samples, one samples was transported in the pneumatic tube transport system and the other was manually transported to the laboratory. The samples were analysed within 30 minutes after the sampling, on the ABL 800 Flex instrument, using the methods potentiometry, amperometry and spectrophotometry. The results were compared using a correlation diagram with a regression line to study the relationship between the parameters. The correlation diagram shown a positive linear correlation and a relationship could be demonstrated for all the parameters (r = 0,929-0,998). If the results from the samples transported manually increased, the results also increased from the samples transported in the pneumatic tube transport system and vice versa. A bar chart was created to visualize differences in the mean values. A difference could be seen in base excess and the mean value increased after transport in the pneumatic tube transport. A two-sided paired t-test was performed to demonstrate any significant difference between the parameters. The t-test demonstrated a significant difference in the oxygen tension (p = 0,04), oxygen saturation (p = 0,04), base excess (p = 0,001) and the standard bicarbonate (p = 0,006) and statistically the values was higher after transport with the pneumatic tube transport system. The mean value for sodium ions decreased after transport in the pneumatic tube transport system and that indicate that hemolysis did not occur. The conclusion of the study was that there is a significant difference between blood gas syringes transported with pneumatic tube transport system and blood gas syringes transported manually, but the differences are not clinically relevant.

The importance of porous materials has risen substantially in the last few decades due to their ability to reduce the size and cost of bioanalytical devices and fuel cells. First, this work aims to describe the fabrication of nanoporous gold (NPG) electrodes that are resistant to electrode passivation due to fibrinogen biofouling in redox solutions. The effect on potentiometric and voltammetric experiments was seen as a deviation from ideal behavior on planar gold electrodes, whereas NPG electrodes were consistently behaving in a Nernstian fashion at low concentrations of ferri-ferrocyanide (£100 mM). An improvement in electrode behavior on NPG electrodes versus planar gold was seen in solutions containing ascorbic acid as well as blood plasma. Second, cost effective NPG electrodes were fabricated using a glass substrate to test the response in the presence of a variety of redox molecules. The optical transparency of these electrodes allowed for microdroplet measurements to be made using an inverted microscope in several redox solutions for validation and subsequent biological applicability. Nernstian behavior was demonstrated for all one- and two-electron transfer systems in both poised and unpoised solutions. All experiments were conducted using volumes between 280 and 1400 pL producing rapid results in less than one minute. Third, in order to decrease the requirement for complex instrumentation, microdroplet fabrication technique was used to create mini-nanoporous gold (mNPG) electrodes on glass capillary tubes. The cylindrical shape of the electrodes allowed for testing in sample volumes of 100 mL. The response to ferri-ferrocyanide, ascorbic acid, cysteine, and uric acid was then investigated with Nernstian behavior shown. However, the mNPG electrodes were insensitive to glucose and hydrogen peroxide. In order to increase the sensitivity of the electrodes, a minimal amount of platinum was electrodeposited onto the NPG surface using a low concentration of platinum salt (0.75 mM) for a short deposition time (2 seconds) producing a Nernstian response to both glucose and hydrogen peroxide. Lastly, to test the viability of crossover applications, the platinum incorporated NPG electrode was employed as a fuel cell anode material, testing their oxidation capability with methanol, ethanol, and formic acid.

A construção de sensor potenciométrico, utilizando Nióbio acoplado a eletrodo de referência de prata/cloreto de prata num mesmo instrumento, possibilita o acompanhamento da variação de potencial que ocorre durante uma reação ácido-base em meio aquoso. Foi utilizado eletrodo de vidro combinado, cuja membrana de vidro foi danificada fisicamente, porém com sua referência interna em pleno funcionamento. O eletrodo de Nióbio foi confeccionado com metal polido ou então com a superfície modificada com óxido eletrodepositado. O crescimento de óxido sobre o Nióbio foi obtido por eletrólise em meio a H3PO4 diluído. O metal ou o par metal/óxido foi fixado no eletrodo de vidro contendo uma solução eletrolítica. O eletrodo de Nióbio não apresenta boa sensibilidade quando utilizado como indicador em potenciometria direta, mas é sensível às variações de potenciais que ocorrem em titulações ácido-base. O eletrodo de Nióbio metálico pode substituir o eletrodo de vidro combinado na determinação do teor de acidez de vinagres.
The construction of potentiometric sensors, using Niobium combined with the reference electrode silver / silver chloride in a single instrument, allows the variation of potential monitoring that occurs during an acid-base reaction in aqueous media. It was used a combined electrode glass, whose glass membrane was damaged physically, but with the internal reference in full operation. The Niobium electrode was made with polished metal or with the surface modified by electrodeposited oxide. The oxide growth was obtained by electrolysis in the H3PO4 diluted media. The metal or metal/oxide was fixed in glass electrode containing a electrolyte solution. The Niobium electrode doesn\'t show sensitivity when used as an indicator in direct potentiometry, but is sensitive to changes of potential that occur in acid-base titrations. The electrode of Niobium metal can replace the glass electrode combined in determining the level of acidity of vinegar.

En les darreres dècades, el món ha experimentat profunds canvis socials i tecnològics. Entre aquests, són destacables les tendències emergents d’anàlisis descentralitzats i de xarxes de sensors, que estan tenint un gran impacte en moltes àrees, especialment en el sistema sanitari. El desenvolupament d’eines per a realitzar anàlisis fora del laboratori de forma robusta, simple i econòmica, serà de gran ajuda per generar, per exemple, eines de diagnòstic assequibles. Per complementar aquestes tendències, aquesta tesis presenta el desenvolupament d’una eina analítica nova per anàlisis descentralitzats, usant paper modificat amb nanotubs de carboni com a substrat i la potenciometria com a tècnica de detecció. Els nanotubs de carboni s’han incorporat amb èxit sobre un paper de filtre convencional, convertint-lo així en conductor, i proporciona’t-li habilitat transductora ió-electró. Amb aquesta plataforma s’han desenvolupat elèctrodes selectius de ions per a diferents ions –mantenint el mateix rendiment analític que els elèctrodes convencionals- així com també un elèctrode de referència. La demostració de que aquesta plataforma pot solucionar un problema analític s’ha dut a terme a través del desenvolupament d’una cel·la potenciomètrica complerta de paper per a la detecció de liti en sang. Aquests elèctrodes també han estat combinats amb èxit amb un potenciòmetre d’identificació per radiofreqüència (RFID), cosa que permet el seu ús de forma descentralitzada. Altres aplicacions possibles, juntament amb les limitacions del sistema es discuteixen en detall. En definitiva, aquest treball obre la possibilitat de substituir sensors convencionals per aquesta plataforma més econòmica, obrint així tota una nova gama d’oportunitats.
En las últimas décadas, el mundo ha experimentado profundos cambios sociales y tecnológicos. Entre los cuáles son destacables las tendencias emergentes de análisis descentralizados y de redes de sensores, que tienen un gran impacto en muchas áreas, especialmente en el sistema sanitario. El desarrollo de herramientas para realizar análisis fuera del laboratorio de forma robusta, simple i económica, será de gran ayuda per generar, para generar, herramientas de diagnóstico asequibles. Para complementar estas tendencias, esta tesis presenta el desarrollo de una herramienta analítica nueva para análisis descentralizados, usando papel modificado con nanotubos de carbono como sustrato y la potenciometría como técnica de detección. Los nanotubos de carbono se han incorporado con éxito sobre un papel de filtro convencional, convirtiéndolo así en conductor, y proporcionándole habilidad transductora ion-electrón. Con esta plataforma se han desarrollado electrodos selectivos de iones para distintos iones manteniendo el mismo rendimiento analítico que los electrodos convencionales- así como también un electrodo de referencia. La demostración de que esta plataforma puede solucionar un problema analítico se ha hecho a través del desarrollo de una celda potenciométrica completa de papel para la detección de liti en sangre. Estos electrodos también se han combinado con éxito con un potenciómetro de identificación por radiofrecuencia (RFID), cosa que permite su uso de forma descentralizada. Otras aplicaciones posibles, junto con las limitaciones sistema se discuten en detalle. En definitiva, este trabajo abre la posibilidad de substituir los sensores convencionales por esta plataforma más económica, abriendo así tota una nueva gama de oportunidades.
During the last decades, the world has undergone deep social and technological changes. Remarkably are the emerging trends of decentralised analysis and sensing networks, which are having a deep impact in many areas, especially in the healthcare system. The development of tools for performing measurements out of the lab in a robust, simple and cost-effective way will be of great help to generate, for example, affordable diagnostic tools. To complement this trends, this thesis presents the development of a novel analytical tool for decentralised measurements, by using paper as a substrate modified with carbon nanotubes (CNT), and potentiometry as detection approach. CNTs have been successfully incorporated over a conventional filter paper making it conductive, and giving to it ion-to-electron transduction capability. Over this platform ion-selective electrodes for different ions have been developed –keeping the same analytical performance as conventional electrodes- as well as a reference electrode. The demonstration that this platform can solve an analytical problem has been proved through the development of a complete paper cell for the detection of lithium in blood. This electrodes have been also combined with a radio frequency identification (RFID) potentiometer, which will allows its use in a decentralised way. Other possible application of this platform together with its limitations are also discussed. All in all, this work opens the possibility to substitute conventional sensors for this low-cost paper sensors, thus unlocking a whole new range of possibilities.

La gran demanda de información en tiempo real, in situ y de calidad, para llevar a cabo el control y la monitorización de múltiples parámetros (bio)químicos en ámbitos como el aeroespacial, medioambiental, industrial, alimentario o biomédico, ha fomentado en los últimos años el desarrollo de instrumentación analítica con un alto nivel de integración, miniaturización y automatización. De esta manera, han aparecido los denominados microsistemas de análisis total (µTAS) o Lab-on-a-Chip (LOC). Así, el trabajo realizado en esta tesis tiene como objetivo principal el desarrollo de microanalizadores automatizados, usando las tecnologías LTCC y de polímeros, para la determinación, mediante medidas potenciométricas y ópticas, de diversos parámetros químicos, en aplicaciones seleccionadas, donde la miniaturización es condición indispensable para poder abordar el problema. Para ello, se han diseñado, construido y evaluado microsistemas donde se han integrado diferentes operaciones unitarias del procedimiento analítico, imprescindibles para la realización de este. Así, en primer lugar se presentan tres dispositivos analíticos desarrollados en el marco de dos proyectos financiados por la Agencia Espacial Europea (ESA) con el objetivo de desarrollar analizadores para monitorizar el proceso de reciclado de agua, y la calidad de esta, en misiones espaciales tripuladas de larga duración. El primero de ellos es un microanalizador potenciométrico robusto, basado en la tecnología LTCC, para monitorizar simultáneamente la presencia de iones potasio y nitrato usando la técnica FIA. El microdispositivo integra, monolíticamente, la microfluídica y el sistema de detección, basado en dos ESIs de membrana polimérica, uno para potasio y otro para nitrato, y un electrodo de referencia de Ag/AgCl serigrafiado. El segundo de ellos, mejora las prestaciones del primero y consiste en un microanalizador, fabricado en COC, para la monitorización simultánea de iones potasio, cloruro y nitrato. Este nuevo dispositivo minimiza la interferencia de cloruro sobre el electrodo de nitrato y miniaturiza y automatiza el sistema de gestión de fluidos incorporando microbombas y microválvulas. El último de ellos es un microanalizador potenciométrico robusto y altamente selectivo fabricado en COC para la determinación de ión amonio. Este integra la microfluídica, un módulo de difusión gaseosa y el sistema de detección en un único sustrato monolítico. El módulo de difusión gaseosa lo compone una membrana hidrófoba de PVDF y el sistema de detección potenciométrico está formado por un electrodo selectivo de ión amonio de membrana polimérica y un electrodo de referencia de Ag/AgCl serigrafiado. También se ha aplicado este último dispositivo al análisis de amonio en muestras acuosas de diversa procedencia (agua de red de distribución y aguas residuales de EDARs, tanto urbanas como industriales) y en muestras de sangre y plasma de pacientes diagnosticados de desordenes en el ciclo de la urea. Otro de los microsistemas analíticos desarrollados, fabricado en COC, incorpora una etapa de difusión gaseosa para la determinación espectrofotométrica de CO2 utilizando un indicador ácido-base colorimétrico. El tamaño reducido del microsistema analítico, unido al tamaño reducido y a la simplicidad del sistema de detección, dotan al equipo global de una gran portabilidad. Se ha aplicado al análisis de CO2 en vino y cervezas y para la monitorización de la acidificación oceánica. Por último, se ha desarrollado un microsistema analítico autónomo y automatizado para la determinación espectrofotométrica de fosfato en aguas residuales. El microanalizador, fabricado en COC, integra un sistema de detección óptica miniaturizado y un sistema de gestión de fluidos automático que le dota de portabilidad y capacidad de funcionamiento autónomo. Todos los microsistemas desarrollados han mostrado unas características analíticas excelentes, cumpliendo los requisitos de las aplicaciones para las que fueron diseñados y demostrando la potencialidad de la miniaturización en los sistemas analíticos.
The high demand for real-time, on-site and quality information to monitor multiple (bio)chemical parameters in areas such as aerospace, environmental, industrial, food or biomedical has promoted the development of an analytical instrumentation with a high level of integration, miniaturization and automation. In this way, the so-called total analysis microsystems (μTAS) or Lab-on-a-Chip (LOC) have appeared. Thus, the main objective of this thesis is the development of automated microanalyzers, using LTCC and polymer technologies, for the determination, using potentiometric and optical measurements, of different chemical parameters in selected applications, where miniaturization is a must to address the problem. For this purpose, different analytical microsystems have been designed, constructed and evaluated where different essential unit operations to carry out the analytical procedure have been integrated. First of all, three analytical devices have been developed in the framework of two projects funded by the European Space Agency (ESA) with the aim of developing analyzers to monitor the water recycling process and its quality in long-term manned space missions. The first one is a robust potentiometric microanalyzer, based on LTCC technology, to simultaneously monitor the presence of potassium and nitrate ions using the FIA ​​technique. The microdevice monolithically integrates the microfluidics and the detection system, based on two ISEs, one for potassium and the other one for nitrate, and a screen-printed Ag/AgCl reference electrode. The second one improves the performance of the first device and consists of a microanalyzer, made of COC, for the simultaneous monitoring of potassium, chloride and nitrate ions. This new device minimizes the chloride interference on the nitrate electrode and miniaturizes and automates the fluid management system incorporating micropumps and microvalves. The last one is a robust and highly selective potentiometric microanalyzer fabricated in COC for the determination of ammonium ion. It integrates the microfluidics, a gas-diffusion module and the detection system into a single monolithic substrate. The gas-diffusion module is composed of a hydrophobic PVDF membrane and the potentiometric detection system consists of an ammonium ion selective electrode and a screen-printed Ag/AgCl reference electrode. The latter device has also been applied to the analysis of ammonia in aqueous samples of diverse origin (drinking water and wastewater from WWTPs, both urban and industrial) and in blood and plasma samples of patients diagnosed with disorders in the urea cycle. Another developed analytical microsystem, made of COC, incorporates a gas-diffusion step for the spectrophotometric determination of CO2 using a colorimetric acid-base indicator. The small size of the device, coupled with the reduced size and simplicity of the detection system, give a high portability to the overall system. It has been applied to CO2 analysis in wine and beers and for the monitoring of ocean acidification. Finally, an autonomous and automated analytical microsystem has been developed for spectrophotometric determination of phosphate in wastewater. The microanalyzer, made of COC, integrates a miniaturized optical detection system and an automatic fluid management system that give it portability and autonomous operation capacity. All microsystems developed have shown excellent analytical features, fulfilling the requirements of the applications for which they were designed and demonstrating the potential of miniaturization in analytical systems.

Dentre as formas alotrópicas do carbono, o grafeno merece destaque. Este material consiste de uma monocamada atômica de carbono sp2 disposta em uma rede bidimensional cristalina hexagonal tipo favo de mel. Uma das formas de se obter o grafeno é pela esfoliação química, que consiste da oxigenação do grafite policristalino em um ambiente altamente oxigenado, formando um produto intermediário chamado de grafeno oxidado (GO). Por este método, gera-se um produto altamente estável e solúvel em água, podendo ser utilizado na construção de filmes ultrafinos. Uma das aplicações possíveis do grafeno oxidado é em sensores e biossensores, área de aplicações de novos materiais que viabilizem o diagnostico rápido, preciso, seletivo e de baixo custo, principalmente os do tipo, point-of-care. O grafeno é um forte candidato, nessa área, devido a sua alta performace e seu baixo custo de processamento. Neste trabalho, a técnica de automontagem eletrostatic layer-by-layer (ELBL) foi utilizada na construção de filmes de grafeno oxidado, juntamente com o policátion dendritico poli(amido amina) geração 4 (PAMAM-G4) em uma plataforma potenciométrica, utilizando um amplificador de instrumentação comercial AD620 como transdutor em um sensor de pH para caracterização da sensibilidade do dispositivo. Diversas técnicas espectroscópicas, óticas e morfológicas foram utilizadas para caracterizar a esfoliação química do grafite e dos filmes automontados. Através destas caracterizações mostrou-se que a esfoliação ocorreu satisfatoriamente concordando com resultados já existentes na literatura. A construção dos filmes ultrafinos ocorreu pela rápida adsorção do GO em camadas alternadas de PAMAM-G4, e o monitoramento do crescimento dos filmes foi realizado utilizando espectroscopia no UV-Vis, onde o crescimento é linear a partir da décima camada. Por microscopia de força atômica, mostrou-se que a adsorção das folhas de grafeno se dá primeiramente pelas folhas de menor número de camada (1 e 2 camadas) de GO e para camadas de número superior tem-se uma morfologia totalmente diferente da primeira. Por espectroscopia no infravermelho, mostrou-se a interação entre os dois polieletrólitos, onde há formação de ligações do tipo cross-linking entre as camadas. Medidas de potenciometria indicam a sensibilidade máxima em torno de 57 mV/pH em um substrato de ouro( sensibilidade Nerstiana), o que evidencia a sua aplicabilidade em sensoriamento e também a sua aplicação em biossensores.
Among the allotropic forms of carbon, graphene deserves special attention. This material consists of one atomic monolayer of sp2 carbon arranged in a two-dimensional hexagonal lattice type, namely \"honeycomb\". One common method to obtain graphene is -=by chemical exfoliation, which consists of oxygenation of polycrystalline graphite in a highly oxygenated medium, forming an intermediate product namely graphene oxide (GO). This method generates a highly stable and water soluble GO that can be used in the fabrication of ultrathin films. Graphene is a strong candidate for sensing, due to its high performance and low cost processing. In this dissertation, GO was obtained via chemical routs and processed in the form of ultrathin films in conjunction with polyamidoamine dendrimer (PAMAM G4) in a layered fashion using the Electrostatic Layer-by-Layer (ELBL). The GO/PAMAM films were deposited on potentiometric platforms and used as pH sensors using a commercial amplifier AD620 instrumentation as the detection technique. GO and the LbL films were characterized via spectroscopic, optical and morphological techniques. Film growth was monitored via UV-Vis spectroscopy and revealed a linear adsorption up to the tenth GO/PAMAM bilayer. AFM analyses revealed that graphene sheets containing 1 or 2 layers occurred adsorbed first on the substrates. Potentiometric measurements indicated a maximum sensitivity of ca. 57 mV/pH for GO/PAMAM films deposited on gold substrates (Nernstian Sensitivity), which demonstrates the applicability of the films in sensing and biosensing.

Ces travaux abordent, d'une part l'étude de la coordination du cuivre(II) et nickel(II) avec un ligand heptadenté tripode, et d'autre part la synthèse et la caractérisation de liquides ioniques dérivés de la bétaïne.Tout d'abord, le ligand heptadenté, le tris[(L)-alanyl-2-carboxamidoéthyl]amine (H3trenala), a été synthétisé sous forme de sel de chlorure ; ses constantes de protonation ainsi que les constantes de stabilité des complexes de Cu(II) et de Ni(II) ont été déterminées par potentiométrie. Des espèces complexes mononucléaires dans lesquels le ligand est protonné ([Cu(H5trenala)]4+, [M(H4trenala)]3+), neutre ([M(H3trenala)]2+) ou déprotonné ([M(H2trenala)]+, [M(Htrenala)]) (M = Cu2+ ou Ni2+) ont été mises en évidence. Seul le Cu(II) donne des espèces dinucléaires dans lesquels le ligand est uniquement déprotonné ([Cu2(H2trenala)]2+, [Cu2(Htrenala)]2+, [Cu2(trenala)]+, [Cu2(trenala)(OH)]). A l'état solide, deux complexes dinucléaires de cuivre(II) ont pu être isolés et caractérisés (IR, UV-Vis, masse électrospray, ATG). L'étude des propriétés catalytiques de ces deux complexes montre une faible activité vis-à-vis de la réaction d'oxydation du catéchol.La seconde partie de ce travail présente la synthèse de liquides ioniques constitués par des synthons cationiques dérivés d'ester de glycine-bétaïne {trialkyl(2-éthoxy-2-oxoéthyl)ammonium (alkyl = éthyl, n-propyl et n-butyl), N-(1-méthylpyrrolidyl-2-éthoxy-2oxoéthyl)ammonium} et des anions inorganiques {bis(trifluorosulfonyl)imide (NTf2-), dicyanamide (Dca-), tétrafluoroborate (BF4-)}. Les influences de la longueur de la chaîne alkyle portée par l'atome d'azote ammonium et de la nature de l'anion associé sur les propriétés physicochimiques telles que la densité, les températures de fusion, de transition vitreuse et de décomposition, la viscosité et les fenêtres électrochimiques, ont été déterminées. De plus, des sels fondus ont pu être générés à partir de ces cations organiques associés aux anions tetrafluoroborate, dicyanamide, hexafluorophosphate (PF6-) et perchlorate (ClO4-), et leurs propriétés physicochimiques ainsi que leurs structures cristallines ont été déterminées.Ensuite, les liquides ioniques hydrophobes sont utilisés pour l'extraction des cations métalliques [Cu(II), Ni(II), Cd(II) et Pb(II)] en phase aqueuse. Cette étude montre que les rendements d'extraction d'ions métalliques, déterminés par mesure de la concentration résiduelle en métal en phase aqueuse, dépendent de la longueur de la chaîne alkyle portée par l'atome d'azote ammonium et des propriétés chélatantes de l'anion. Les rendements les plus élevés ont été obtenus avec les liquides ioniques dont l'anion possède des propriétés chélatantes. L'étude du transfert du métal montre qu'il est dépendant de l'hydrophobicité du synthon cationique. Une augmentation de l'hydrophobicité du synthon cationique conduit à une augmentation du rendement d'extraction, tout en limitant l'échange ionique et en privilégiant une extraction par paires d'ions. Enfin, l'électrodéposition en phase liquide ionique et la désextraction liquide-liquide des ions métalliques ont été étudiées
This work deals with copper(II) and nickel(II) complexation of a polydentate tripodal ligand and with, on a second part, the synthesis and characterization of ionic liquids derived from betaine and their use in liquid-liquid extraction.On the first part, a heptadentate ligand, tris[(L)-alanyl-2-carboxamidoethyl]amine (H3trenala), has been synthesized as its tetrahydrochloride salt; its protonation constants and the stability constants of the copper(II) and nickel(II) chelates have been determined by potentiometry. Mononuclear species with protonated, neutral, or deprotonated forms of the ligand, [Cu(H5trenala)]4+, [M(H4trenala)]3+, [M(H3trenala)]2+, [M(H2trenala)]+, and [M(Htrenala)] (M=Cu2+ and Ni2+) have been detected in all cases, while only Cu2+ gives dinuclear [Cu2(H2trenala)]2+, [Cu2(Htrenala)]2+, [Cu2(trenala)]+, and [Cu2(trenala)(OH)] species. Two dinuclear copper(II) complexes have been prepared and characterized by spectroscopic techniques (IR, UV-Vis, mass electro-spray) and thermogravimetric analysis. These two dinuclear copper(II) complexes have revealed weak catalytic activity in catechol oxidation.On the second part, a series of salts based on ethyl ester betaine derivatives[trialkyl(2-ethoxy-2-oxoethyl)ammonium or N-(1-methylpyrrolidyl-2-ethoxy-2-oxoethyl)ammonium cations] with alkyl chains [ethyl, n-propyl and n-butyl] have been synthesized. These cations generate hydrophobic ionic liquids with bis(trifluoromethylsulfonyl)imide, tetrafluoroborate or dicyanamide anions. The influence of the alkyl chain length and the chemical nature of the counteranion on physicochemical properties such as density, melting point, glass transition and decomposition temperatures, viscosity, and electrochemical window have been investigated. In addition, molten salts have been generated from these organic cations with hexafluorophosphate, perchlorate, tetrafluoroborate or dicyanamide anions. Their physicochemical properties and crystal structure have been investigated.The extraction of the different metal cations (Cu2+, Ni2+, Cd2+ and Pb2+) in aqueous solution by hydrophobic ionic liquids synthesized was performed. The extraction yields, determined by the measurements of the residual metal concentration in aqueous solution, depend not only the length of the alkyl chain of the ammonium but also on the nature of the associated anion. The most promising results are obtained with ILs whose anion has a chelating ability. The mechanism of metal transfer has been studied and was related to the hydrophobicity of the cationic synthon. Increasing the hydrophobicity of the cationic synthon leads to an increase of extraction yield, thus limiting the ion exchange and promoting ion pairing extraction. Electrodeposition in ionic liquid phase and liquid-liquid desextraction of metallic ions have also been investigated

Un gran nombre de plataformes de detecció biològica han incorporat materials nanoestructurats com una estratègia per a millorar diversos paràmetres operacionals i de qualitat tals com reduir els temps d'anàlisis i els límits de detecció. Les tècniques electroquímiques de detecció es prefereixen sobre altres tècniques ja que presenten una sèrie d'avantatges com a rapidesa, facilitat de maneig, cost reduït i la reduïda mida dels detectors comercials. Entre les tècniques electroquímiques, les metodologies més simples, comunes i més fàcils de transportar són aquelles basades en la potenciometria. La nova tendència seguida amb els elèctrodes potenciomètrics d'estat sòlid representa una eina atractiva en l'anàlisi de mostres líquides en temps real. No obstant això, fins avui ha estat difícil dur a terme la detecció electroquímica directa de bacteris i proteïnes, sense utilitzar marcadors químics, donat que les interaccions receptor‐bacteri i receptor‐proteïna no produeixen un senyal elèctric mesurable. En aquesta tesi, es demostra per primera vegada la detecció potenciomètrica en temps real de bacteris i proteïnes relacionades amb diverses malalties. Aquesta tasca va ser duta a terme mitjançant el disseny d'una plataforma universal de detecció utilitzant nanotubs de carboni com a transductors potenciomètrics i aptàmers com a elements de reconeixement molecular. Les excel•lents propietats de transducció ofertes pels nanotubs de carboni combinades amb la gairebé il•limitada possibilitat dels aptàmers de ser dissenyats in vitro per reconèixer ions, proteïnes, virus i bacteris converteix aquesta plataforma en una eina amb possibilitats inesgotables de detecció biològica en temps real.
Un gran número de plataformas de detección biológica han incorporado materiales nanoestructurados como una estrategia para mejorar varios parámetros operacionales y de calidad tales como reducir los tiempos de análisis y los límites de detección. Las técnicas electroquímicas de detección se prefieren sobre otras técnicas debido a que presentan una serie de ventajas tales como rapidez, facilidad de manejo, coste reducido y el reducido tamaño de los detectores comerciales. Entre las técnicas electroquímicas, las metodologías más simples, comunes y más fáciles de transportar son aquellas basadas en la potenciometría. La nueva tendencia seguida con los electrodos potenciométricos de estado sólido representa una herramienta atractiva para el análisis de muestras líquidas en tiempo real. Sin embargo, hasta hoy ha sido difícil llevar a cabo la detección electroquímica directa de bacterias y proteínas sin ULTRASENSITIVE DETECTION OF PATHOGENS IN REAL‐TIME POTENTIOMETRIC BIOSENSORS BASED ON SINGLE‐WALLED CARBON NANOTUBES AND APTAMERS utilizar marcadores químicos, dado que las interacciones receptor‐bacteria y receptor‐proteína no producen una señal eléctrica medible. En esta tesis, se demuestra por primera vez la detección potenciométrica en tiempo real de bacterias y proteínas relacionadas con varias enfermedades. Esta tarea fue llevada a cabo mediante el diseño de una plataforma universal de detección utilizando nanotubos de carbono como transductores potenciométricos y aptámeros como elementos de reconocimiento molecular. Las excelentes propiedades transductoras de los nanotubos de carbono combinadas con la casi ilimitada posibilidad de los aptámeros de ser diseñados in vitro para reconocer iones, proteínas, virus y bacterias convierte esta plataforma en una herramienta con posibilidades inagotables de detección biológica en tiempo real.
Numerous biosensing platforms have incorporated nanostructured materials as a strategy for improving several performance and operational parameters such as reducing the limits of detection or the assay times in both pathogen and protein detection. Electrochemical sensing techniques are preferred over other detection methods because they present a series of advantages such as rapid response, ease of use, low‐cost and small sized commercial detectors. Among the electrochemical techniques, the simplest, most widespread and fieldportable methodologies are based on potentiometry. The new wave of potentiometric solidstate electrodes represents an attractive tool for real‐time bioanalysis in liquid samples. However, to date, it has been difficult to carry out the specific and direct electrochemical detection of whole living bacterial cells or disease‐related proteins without chemical labelling because the interaction receptor‐bacteria/receptor‐protein does not provide a measurable electrochemical signal. In this Thesis, the real‐time potentiometric detection of bacteria and disease‐related proteins is demonstrated for the first time. To accomplish such a challenging task, a novel and universal biosensing platform is designed using single‐walled carbon nanotubes as potentiometric transducers, and aptamers as biorecognition elements. The excellent potentiometric transduction properties of carbon nanotubes combined with the quasi‐unlimited capability of aptamers (RNA and DNA synthetic oligonucleotide segments) to be tailored in vitro against ions, proteins, viruses and bacteria converts such a platform into a

Foram estudados os equilíbrios dos complexos de Mn (II) com íons azoteto, em meio aquoso, por método potenciométrico indireto, através de medidas de pH, em meio de azoteto 0 a 1,8 M, e a 25,0 ºC, utilizando força iônica 2,00 M mantida com perclorato de sódio. Nas diferentes concentrações de íon metálico empregadas, 20, 40, 60, 80 e 100 mM, obteve-se uma mesma curva de formação de número médio de ligantes vs. concentração de ligante livre, o que configura a inexistência de complexos polinucleares nessas condições experimentais. Os valores de número médio de ligantes n¯, e de concentração de ligante livre, [L], foram utilizados para a integração de função de Bjerrum, obtendo-se a função de Fronaeus, F0(L), a partir da qual calcularam-se, por métodos gráficos e matemáticos, as quatro sucessivas constantes globais de equilíbrio: β1 = 4,15 ± 0,02 M-1 , β2 = 6,61 ± 0,04 M-2 , β3 = 3,33 ± 0,02 M-3 , β4 = 0,63 ± 0,01 M-4 . Avaliando os valores das constantes, observa-se que os complexos formados são fracos e, em obediência à regra de Irving e Williams, são menos estáveis que os complexos de cobalto (II) e de níquel (II). Em concentrações de ligante superiores a 1M há condições para lenta oxidação espontânea dos complexos de manganês(II) a manganês(III) com significativas mudanças espectrais.
The equilibria of complex formation between manganese(II) cations and azide anions were studied in aqueous medium by an indirect potentiometric method, at 25°C and ionic strengh 2.0 M (NaClO4). The equilibrium data were based on pH measurements of Mn(II) in N3¯/HN3 buffers. Metal ion concentration changing from 20 to 100 mM have defined one single formation curve of n_ (Bjerrum function) vs. [N 3 ¯ ] which is an evidence that only mononuclear species ara present in the working solutions. Integration of the formation curve from the best n¯vs. [N3¯] data leads to Fronaeus function data. They were properly treated to obtain the formation by a variety of methods (graphic and mathematical). The best set formed is: β1 = 4,15 ± 0,02 M-1 , β2 = 6,61 ± 0,04 M-2 , β3 = 3,33 ± 0,02 M-3 , β4 = 0,63 ± 0,01 M-4 . The complex are weaks and are is agreement with the Irving and Williams rule, i. e., less stable than the corresponding complexes of Ni(II) and Co(II). At ligand concentration higher t than 1,0 M there were conditions for a slow spontaneous oxidation of manganese(II) complexes to manganese to manganese(III), with remarkable spectral changes.

Os efeitos terapêuticos dos sais de lítio são comprovados no tratamento de pacientes com depressão, certos tipos de câncer e transtornos bipolares de humor. A dosagem de lítio deve ser cuidadosamente controlada em cada paciente já que excessos na dosagem podem conduzir a danos irreversíveis no sistema nervoso e nos rins. Sendo assim é interessante produzir métodos de baixo custo, simples e rápidos que permitam o monitoramento desse íon. Portanto no presente trabalho foi estudado o desempenho potenciométrico de um eletrodo compósito de pasta de carbono modificado com óxido de manganês tipo espinélio dopado com cobalto (III). O eletrodo de pasta de carbono modificado foi preparado pela mistura de 55% (m/m) de pó de grafite, 20% (m/m) de aglutinante (óleo mineral) e 25% (m/m) de óxido de manganês dopado com cobalto (III) (Li1,05Co0,02Mn1,98O4.). O desempenho eletroquímico do eletrodo foi estudado através de voltametria cíclica (etapa de ativação) e cronopotenciometria (i=0) (etapas de estabilização e adição de padrão). Na caracterização eletroquímica do eletrodo estudou-se a melhor concentração de íons lítio para ativação do sensor, bem como a melhor velocidade de varredura, tempo de estabilização, pH, intervalo linear de resposta, limite de detecção e possíveis íons interferentes. Encontrou-se um limite de detecção de 3,98 x 10-6 mol L-1, intervalo linear de resposta de 1,82 x 10-4 mol L-1 a 1,62 x 10-3 mol L-1, pouca interferência dos íons estudados (Na+, K+, Rb+, Cs+, Mg+2, Ca+2 e Ba+2) sendo a interferência proporcional ao raio iônico dos íons interferentes e sensibilidade de 97,90 mV dec-1. Esse valor de sensibilidade classifica o eletrodo estudado como tendo resposta supernerstiniana o que pode ser atribuído à coexistência de sítios de troca iônica e sítios redox no processo de inserção/extração dos íons lítio na matriz do óxido de manganês. A substituição parcial dos íons Mn pelos íons Co provoca uma diminuição no parâmetro de célula unitária do óxido, o que melhora a estabilidade da estrutura durante o processo de inserção/extração de íons lítio fornecendo maior sensibilidade e propiciando maior seletividade.
The therapeutic effects of lithium salts have been proved useful, as an example given, in the treatment of patients who presents depressive behavior, bipolar disorder and certain types of cancer. The lithium dosage for each patient has to be carefully controlled because an excessive dose can produce irreversible damages to the nervous system and the kidneys. Therefore is interesting produce low cost, simple and quick methods to allow the monitoring of this ion. Hence in this work, the performance of a composite potentiometric carbon paste electrode modified with spinel type manganese oxide doped with cobalt (III) (Li1,05Co0,02Mn1,98O4) was studied. The modified carbon paste electrode was prepared by mixing 55% (w / w) of graphite powder, 20% (w / w) binder (mineral oil) and 25% (m / m) manganese oxide doped with Cobalt (III). The potentiometric performance of the electrode was studied by cyclic voltammetry (activation step) and potentiometry - zero current (stabilization and standard addition steps). The electrochemical characterization of the electrode consisted of the studies of the optimal concentration of lithium ions for activation of the sensor, as well as the best scan rate, stabilization time, pH, linear response range, detection limit and possible interfering ions. In pH = 10, the better one chosen for this study, it was found a detection limit of 3.98 x 10-6 mol L-1, a linear response range from 1.82 x 10-4 mol L-1 to 1.62 x 10-3 mol L-1, low interference from the studied ions (Na+, K+, Rb+, Cs+, Mg+2, Ca+2 e Ba+2), which is proportional to their ionic radius and sensitivity of 97,90 mV dec-1. This high sensitivity value can be attributed to the coexistence of ion exchange sites and redox sites in the insertion / extraction of lithium ions in the manganese oxide matrix process. The best working pH was around 10, as opposed to working with similar materials found in the literature. This can be explained by the substitution of manganese for cobalt (III) in the structure of the spinel type manganese oxide. This substitution causes a decrease in the unit cell parameter of the oxide, which improves the stability of the structure during the process of insertion / extraction of lithium ions and resistance to change in alkaline solutions.

In part 1 of this thesis, the antidiabetic activity of a series of novel oxovanadium(IV) complexes was investigated. A range of bidentate N,O-donor ligands, which partially mimic naturally occurring bioligands, were prepared and reacted with the vanadyl ion to form the corresponding bis-coordinated complexes. Initially, 2-(2ˊ-hydroxyphenyl)-1R-imidazoline (where R = H, ethyl and ethanol) ligands were prepared. The aqueous pH-metric chemical speciation was investigated using glass electrode potentiometry which allowed for the determination of protonation and stability constants of the ligands and complexes, respectively. The species distribution diagrams generated from this information gave an indication of how the complexes might behave across the broad pH range experienced in the digestive and circulatory systems. This information was used to create an improved 2nd generation of ligands that were constructed by combining the imidazole and carboxylic acid functionalities. These corresponding bis[(imidazolyl)carboxylato]-oxovanadium(IV) complexes displayed a broader pH-metric stability. Both sets of complexes improved glucose uptake and reduced coagulation in vitro. In part 2 of this thesis, a range of homogeneous and heterogeneous oxovanadium(IV) catalysts were prepared. Firstly, Merrifield beads were functionalized with ligands from Part 1 and then reacted with vanadyl sulfate to afford the corresponding heterogeneous catalysts. These displayed promising catalytic activity for the peroxide facilitated oxidation of thioanisole, styrene and ethylbenzene as well as the oxidative bromination of phenol red. Smaller imidazole-containing beads with higher surface areas than the Merrifield beads were prepared by suspension polymerization. These beads similarly demonstrated excellent catalytic activity for the oxidation of thioanisole and were highly recyclable. In attempt to increase the exposed catalytic surface area, while retaining the ease of separation achieved in the before mentioned systems, micron to nano sized electrospun fibers containing coordinating ligands were fabricated. The corresponding oxovanadium(IV) functionalized fibers were applied to the oxidation of thioanisole using a continuous flow system. The flexible and porous nature of the fiber mats was well suited to this approach. After optimization of the reactant flow rate and catalyst amount, near quantitative (> 99%) oxidation was achieved for an extended period. In addition, leaching of vanadium was mitigated by modification of the attached ligand or polymer material.

El diagnóstico rápido de la mayoría de las enfermedades tiene una importancia vital para proporcionar el remedio adecuado y, por lo tanto, el control de problemas de salud. La detección rápida y selectiva de biomoléculas grandes, específicamente proteínas, es uno de los objetivos importantes en este campo. Las técnicas basadas en inmunoensayos son las más comúnmente utilizadas, aunque requieren un marcaje específico. Por lo general, estos métodos también requieren personal altamente capacitado y equipos complejos que se traduce en una metodología relativamente cara y lenta. En la presente tesis aportamos por primera vez un nuevo tipo de aptasensores potenciométricos de estado sólido basados en nanotubos de carbono que pueden detectar analitos grandes, como por ejemplo proteínas, de manera rápida (casi instantánea), selectiva, y sensible sin necesidad de marcaje químico. Los sensores desarrollados responden correctamente a la proteína analito (α-trombina humana) dentro de los niveles fisiológicos en el suero humano.
Rapid diagnosis of most illnesses has a vital importance for providing the appropriate cure and hence controlling public health concerns. Fast and accurate detection of large biomolecules, specifically proteins, is one of the major steps regarding the subject. Over recent years, several detection methodologies have been developed. However, almost all of the developed methods either required very complex techniques to be applied, or a long time to obtain the results. The most commonly used techniques were specific label requiring immunoassays. They generally require highly trained staff and complex equipment which results in an expensive and relatively slow methodology. With the present thesis we report a new type of label-free potentiometric solid state carbon nanotube based aptasensors that can detect large analytes, as case example proteins, in a rapid (almost instantaneous), selective and sensitive way, for the first time. The developed sensors successfully responded to analyte protein (human α-thrombin) within physiological human serum levels.

Abstract This thesis is a summary of five papers, containing equilibrium and structure studies of aqueous molybdate and peroxomolybdate species. Some of the peroxomolybdate species have also been studied in terms of their dynamic and catalytic properties. The primary objective was to characterize species with potential catalytic activity, with emphasis on thebleach process of kraft pulp. For this, potentiometry, EXAFS and 17O, 31P, 1H and 95 Mo NMR have been used. The molybdate speciation in 0.300 M Na2(SO4) medium was found to differ from that in 0.600 M Na(Cl) medium, in that the uncharged monomeric molybdate species H2MoO4 was stronger in the sulphate medium, while highly charged species, such as Mo7O24 6-, became somewhat less pronounced. Diperoxomolybdate species, (MoX2)n (X = peroxo ligand, n = 1-2), dominated the peroxomolybdate systems when sufficient peroxide was available. Both sulphate and chloride coordinated to molybdenum in the presence of hydrogen peroxide and these species were more inert than diperoxomolybdate species without coordinated medium anions. Chemical exchange rates increased upon protonation. A dimeric triperoxomolydate species was the only species found that contained more than two peroxo groups per molybdenum atom. At low concentrations of hydrogen peroxide, monoperoxoheptamolybdate species, Mo7X, were found. Phosphate was found to coordinate relatively weakly to molybdate in the presence of peroxide. Species with four different nuclearities, i.e. (MoX2)nP (n = 1-4), were found. At excess of peroxide, no molybdophosphates were present. Chemical exchange rates were found to be substantially lower than in the peroxomolybdate system. The aqueous monomeric diperoxomolybdate species retain the pentagonal bipyramidal seven-coordination found in the solid state, although with increased bond lengths. Sulphate seems to coordinate to molybdenum in a monodentate fashion by replacing an oxygen atom. Chloride probably coordinates by replacing an oxygen atom as well. For the dimeric diperoxomolybdate species, a single oxygen-bridge was proposed. Conjugated carbon double bonds in the side chains of lignin model compounds were found to be hydroxylated or epoxidised by peroxomolybdate species. The addition of phosphate did not affect the type or yield of oxidation products noticeably. It was also shown that hydrogen peroxide, in the absence of molybdate, did not react to any noticeable extent with the lignin model compounds under these conditions.

L’objectiu principal d’aquesta tesi és l’exploració de noves fronteres en l’àrea de sensors químics. Primerament, a través del desenvolupament de nous enfocs per construir sensors químics vestibles. Seguidament, a través de la generació de noves maneres de sensar electròlits en mostres reals. La potenciometria i la detecció òptica seran les tècniques utilitzades. L’ús de la potenciometria cap al 1900, amb els elèctrodes selectius de ions (ESI), ha anat canviant i la revolució va començar amb la miniaturització d’aquests ESI amb l’aparició de la necessitat de sensors per monitoritzar el nostre estat de salut, juntament amb la tendència de desenvolupar sensors vestibles. Aquesta tesi, llavors, ha estat el punt d’inici per al desenvolupament de sensors incorporats en plataformes vestibles, per acabar mesurant electròlits en fluids biològics. També, aquesta tesi s’ha focalitzat en la millora de les membranes selectives polimèriques, específicament per un analit. Durant la última dècada, hi ha hagut un avenç considerable i recerca de nous receptors per molècules clínicament rellevants present en el nostre cos. Per exemple, la introducció d’un nou receptor artificial (calix[4]pyrrole) per creatinina ha sigut un resultat molt important d’aquesta tesi. La creatinina és la segona molècula més detectada rutinàriament analitzada després de la glucosa, fet el qual probablement pot obrir la porta cap al mercat després d’aquesta tesi. Finalment, la potenciometria no ha estat l’única tècnica utilitzada en aquesta tesi, sinó que també s’ha utilitzat la tècnica òptica. El repte més important, demostrat en aquesta tesi, és la detecció d’anions difícilment detectables amb la potenciometria, com per exemple l’anió sulfat.
El objetivo principal de esta tesis es la exploración de nuevas fronteras en el área de sensores químicos. Primeramente, a través del desarrollo de nuevos enfoques para construir sensores químicos vestibles. Seguidamente, a través de la generación de nuevas maneras de sensar electrolitos en muestras reales. La potenciometría y la detección óptica serán las técnicas utilizadas. El uso de la potenciometría allá en el 1900, con los electrodos selectivos de iones (ESI), ha seguido un proceso de cambio y la revolución empezó con la miniaturización de estos ESI con la aparición de la necesidad de sensores para monitorizar nuestro estado de salud, juntamente con la tendencia de desarrollar sensores vestibles. Esta tesis, entonces, ha sido el punto de inicio para el desarrollo de sensores incorporados en plataformas vestibles, para medir electrolitos en fluidos biológicos. También, esta tesis se ha focalizado en la mejora de las membranas selectivas poliméricas, específicamente para un analito. En la última década, ha habido un avance considerable e investigación de nuevos receptores para moléculas clínicamente relevantes presentes en nuestro cuerpo. Por ejemplo, la introducción de un nuevo receptor artificial (calix[4]pyrrole) para creatinina ha sido un resultado muy importante para esta tesis. La creatinina es la segunda molécula más detectada rutinariamente analizada después de la glucosa, hecho que probablemente puede abrir la puerta al mercado después de la tesis. Finalmente, la potenciometría no ha sido la única técnica utilizada en esta tesis, sino que también se ha utilizado la técnica óptica. El reto más importante, demostrado en esta tesis, es la detección de aniones difícilmente detectables con la potenciometría, como per ejemplo el anión sulfato.
The main objective of this thesis is the exploration of new frontiers in the area of chemical sensors. First, through the development of novel approaches to build wearable chemical sensing devices. Second, through the generation of new sensing approaches to determine electrolytes in liquid samples. Potentiometry as well as optical detection techniques will be used. Since potentiometry was firstly used at the beginning of 1900, with classical ion-selective electrodes (ISEs), this technique have constantly been changing and the revolution of this technique started with the miniaturization of these ISEs in combination with the real need of sensors for monitoring our health status, which has merged in a new trend to develop wearable sensors. This thesis has, then, been the starting point to develop potentiometric sensors embedded in wearable platforms, being finally used for measuring electrolytes in biological fluids. Also, this thesis has been focused on the improvement of the ion-selective polymeric membrane sensitive to one specific electrolyte. In the last decade, there has been a considerable advance and research of new receptors for clinically relevant molecules present in our body. For example, the introduction of a new artificial receptor (calix[4]pyrrole) for creatinine has been a significant milestone in this thesis. Creatinine is the second most important molecule routinely analyzed after glucose, thus likely to open a path to the market beyond this thesis. Finally, potentiometry has not been the only technique used in this thesis but also optical technique. The real challenge, overcome in this thesis, has been to sense anions selectively, especially the ones that currently are hardly measured with potentiometry, such as for example sulphate.

Apatites are a diverse class of phosphate minerals that are important in a great variety of natural and industrial processes. They are, for example, used as raw material in fertiliser production and in the remediation of metal-contaminated soils. Hydroxyapatite Ca5(PO4)3OH, (HAP) and fluorapatite Ca5(PO4)3F, (FAP) are similar to the biological apatite that is the main constituent of mammalian bone and teeth, and they are therefore promising materials for artificial bone and tooth implants. This thesis is a summary of four papers with focus on dissolution and surface complexation reactions of HAP and FAP in the absence and presence of both organic ligands and the natural and commonly occurring iron oxide goethite (α-FeOOH). The dissolution and surface complexation of HAP and FAP was investigated with a combination of different techniques. Potentiometric acid/base titrations and batch experiments were combined with X-ray Photoelectron Spectroscopy (XPS) and Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) Spectroscopy to generate dissolution and surface complexation models for both apatites. The results from these studies showed that both apatites form surface layers that are different from their bulk compositions when equilibrated in aqueous solutions. The modeling efforts predicted speciation of these surfaces as well as the concentration of the dissolution products in the solution. The interaction between organic ligands and the apatite surfaces was also investigated and the results from this study show that the organic ligands form outer-sphere complexes on the apatite surfaces over a large pH interval, and that this adsorption enhances the dissolution of apatites. The presence of goethite also enhances the dissolution of FAP as it acts as a sink for the phosphate released from FAP. Phase transformation in this system was detected using ATR-FTIR as the phosphate adsorbed to the goethite surface precipitates as FePO4 (s) after approximately 15 days of reaction time. This changes the speciation, and possibly also the bioavailability of phosphate in this two-mineral system.

The thesis deals with observation of cells parameters. One of the potential solutions for observing the characteristics of cells are utilization the electrochemical analyse called voltametry. Its fundamental consists of loading variable voltage in between two electrodes dipped in electrolytic solution and monitoring flowing current. The point of the thesis is to build up the measuring workplace, which can provide this measurement. We suggest utilization of modern laboratory technique and connection the measuring instruments with PC. The first part of the thesis deals with theoretical knowledge of used functions and describes theirs mathematics definitions. The second part deals with proceeding of workplace realization, instrument connection with PC and development application in computer’s language. Result is measuring workplace, which can provide observing cells according to entered parameters.

Nous sensors electroquímics per a analisis decentralitzats és una tesis que emmarca diferents aspectes del desenvolupament de sensors potenciomètrics, des de la seva fabricació, el diseny adequat, i finalment, la seva aplicabilitat en escenaris reals. En el context actual, l'evolució de la tecnologia, especialment l'aparició a nivell global d'internet, i la disponibilitat d'aquesta a baix cost han permès la creació d'eines que ens permeten connectar el món físic i, en el cas d'aquesta tesis, el món químic a la xarxa. Aquesta connexió aporta un nou grau dins l'escala de valor per a la societat actual. Concretament, aquesta aportació tecnològica va adreçada a superar els nous reptes de l'actualitat, com poden ser la sostenibilitat del sistema sanitari a causa de l'embelliment de la societat, el control medioambiental, així com també mantenir la seguretat per a la societat del benestar del futur. Així doncs, aquesta tesis presenta solucions efectives per al desenvolupament d'eines de captació d'informació que serviràn per nudrir a la societat de major coneixement. Conseqüentment, produint nous negocis al voltant, de la fabricació, processament i creació de valor entorn a aquestes dades. La recerca i desenvolupament de sensors potenciomètrics integrats a la roba per detectar els nivells d'electròlits i sensors senzills de paper per a la determinació de biomolècules, com la glucosa, són alguns dels objectius aconseguits en aquesta tesis. A més a més, sensors integrats en globus permeten l'estudi de les seves propietats mecàniques i electroquímiques, així com també, aporten noves solucions a problemes reals. Totes aquestes aplicacions serveixen de portals de captació d'informació química cap a la integració dins la nova societat de la informació.
Nuevos sensores electroquímicos para analisis decentralizados es una tesis que enmarca diferentes aspectos del desarrollo de sensores potenciométricos, desde su fabricación, el diseño adecuado, i finalmente, su aplicabilidad en escenarios reales. En el contexto actual, la evolución de la tecnología, especialmente la aparición a nivel global de internet, y la disponibilidad de esta a bajo coste han permitido la creación de herramientas que nos permiten conectar el mundo físico y, en el caso de esta tesis, el mundo químico a la red. Esta conexión aporta un nuevo grado dentro la escala de valor para la sociedad actual. Concretamente, esta aportación tecnológica va dirigida a superar los nuevos retos de la actualidad, como pueden ser la sostenibilidad del sistema sanitario a causa del envejecimiento de la poblacion, el control medioambiental, así como también mantener la seguridad para la sociedad del bienestar del futuro. Entonces, esta tesis presenta soluciones efectivas para el desarrollo de herramientas de captación de información que servirán para nutrir a la sociedad de un mayor conocimiento. Por consiguiente, produciendo nuevos negocios alrededor, de la fabricación, procesado i creación de valor en los datos obtenidos. La investigación y desarrollo de sensores potenciométricos integrados en la ropa para detectar los niveles de electrolitos y sensores simples en papel para la determinación de biomoléculas, como la glucosa, son algunos de los objetivos conseguidos en esta tesis. Además, sensores integrados en globos permiten el estudio de sus propiedades mecánicas y electroquímicas, así como, aportando nuevas soluciones a problemas reales. Todas estas aplicaciones sirven de portales de captación de información química hacia la integración dentro de la nueva sociedad de la información.
ew Electrochemical Sensors for Decentralized Analysis is a thesis that wisely discuss the developments of potentiometric sensors, from the fabrication step, the use of a suitable design, to the applicability in real scenarios. Nowadays, the evolution of technology, specially the creation of the global internet network, and the low-cost availability of such technology have allowed the development of tools that connect the physical world and, addressed in this thesis, the chemical world into the network. This connection adds a new level in the value chain for the present society. Precisely, this technology approach is focus on circumvent new present challenges of society. For instance, sustainability of the healthcare system caused by the population aging, environmental monitoring, as well as, keep security and safety to the welfare of society of the future. Therefore, this thesis presents successful solutions for the development of tools to gather chemical information. This information will nurture society with high-value knowledge. Accordingly, new business development from, sensing products, data treatment and information management are going to be created. Research and development of potentiometric sensors integrated into garments for electrolyte detection and simple sensors built in paper for biomolecules determination, such as glucose, and liquid monitoring, such as sweat, are some of the accomplished objectives from this thesis. Furthermore, balloon-embedded sensors allow the study of the mechanical and electrochemical properties of the electrodes, as well as, contributing with new solutions to real problems. All the applications developed in this thesis are utilized as gateways for chemical information acquisition towards the integration into the new information society.

O presente trabalho procura dar continuidade a uma das linhas de pesquisa desenvolvida pelo Grupo de Química Analítica do Instituto de Química da Universidade de são Paulo: o estudo da formação de complexos. O sistema Hg(II) / S2O2-3 foi analisado potenciometricamente, com a finalidade de identificar o número de complexos formados, assim como estimar as constantes de estabilidade envolvidas no fenônemo de complexação. Tal equilíbrio foi levado a termo a 25,0 ± 0,1°C, e força iônica 2,00M, sendo detectados quatro espécies complexas. O modelo matemático que melhor se ajustou aos dados experimentais fornecidos pelo sistema, conta com os seguintes valores para as constantes globais de formação: β1 1 = x 1024 M-1 (valor atribuído) β2 = (8,0 ± 2,8) x 1027 M-2 β3 = (1,71 ± 0,03) x 1030 M-3 β4 = (3,07 ± 0,77) x 1030 M-4. Na região de baixa concentração analítica de ligante, 5mM, o acesso experimental foi limitado pela precipitação de sulfeto mercúrico sendo impossível obter informaçôes sobre a primeira espécie. O comportamento do mercúrio no sistema Hg(II) / S2O2-3 foi estudado de uma forma mais abrangente, sendo estendido ao meio não complexante, onde o equilíbrio de dismutação do cátion mercuroso governa. Nas mesmas condições de temperatura e força iônica anteriores, foram obtidos alguns parâmetros desse equilibrio, a saber: - potenciais formais de eletrodo: Eo\'Hg(I) / Hg(O) = ( 0,456 ± 0,014 ) V Eo\'Hg(II) / Hg(O) = ( 0,559 ± 0,0016) V Eo\'Hg(III) / Hg(I) = ( 0, 6625 ± 0,0023 ) V - constante do equilibrio heterogêneo: Qp (potenciométrica) = (3 ± 1) x 103 Adicionalmente, foram realizados estudos eletrogravimétricos sobre o mecanismo de oxidação coulométrica do mercúrio metálico, em diversos eletrólitos suporte, merecendo destaque a estabilização do Hg(I) por cloreto, e do Hg (II) por tiossulfato, mostrando que a transferência eletrônica é um processo por etapas. Complementando o estudo do sistema, a potencialidade análitica do tiossulfato na determinação dos cátions do mercúrio foi confirmada em titulações potenciométricas.
The present work belongs to one of the topics developed by the Analytical Chemistry Group in the Chemistry Institute of the são Paulo University: the study of complex formation equilibrium. The Hg(II)/S2O2-3 system was potentiometrically analysed with the purpose of identifying the number of formed complexes as well as computing their stability constants. Such equilibria study was performed at a 25.0 ± 0.1ºC temperature and 2.00 M ionic strengh, mantained with NaClO4. Four stepwise complexes have been detected by a calculus procedure based on non-linear regression. The best formation constants set is: β1 1 = x 1024 M-1 (arbitrary value) β 2 = (8,0 ± 2,8) x 1027 M-2 β3 = (1,71 ± 0,03) x 1030 M-3 β4 = (3,07 ± 0,77) x 1030 M-3. At lower ligand concentration, nearly 5mM, the experimental access was limited by the mercuric sulphide precipitation, being impossible to achieve data on the first specie. The mercury performance in the Hg(II)/S2O2-3 system was more widely studied with concern to the non-complexing media, where the disrnutation of mercurous cation leads. With the same previous temperature and ionic stengh conditions, some equilibria parameters have been determined: - electrode potentials: Eo\'Hg(I) / Hg(O) = ( 0,456 ± 0,014 ) V Eo\'Hg(II) / Hg(O) = ( 0,559 ± 0,0016) V Eo\'Hg(III) / Hg(I) = ( 0, 6625 ± 0,0023) V - heterogeneous equilibria constant: Qp = (3 ± 1) x 103. Electrogravimetric studies about the coulometric oxidation mecanism of metallic mercury have also been executed. The oxidation was carried out at several suporting electrolites, regarding the Hg(II) stabilization by the tiossulphate anion, and the Hg(I) by chloride, showing that the electrochemical transfer occurs in a step by step process. In addition to system study, the analytical potentiality of the tiossulphate on the determination of mercury cationic species was confirmed by potentiometric titulations.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
The purpose of this investigation was to propose the determination of ascorbic acid in pharmaceutical drug samples, by means of a laboratorymade potentiometric system that allowed the study of oscillating reactions. The method is based in the effect of ascorbic acid in oscillation pattern of Belousov-Zhabotinskii reaction. The experimental conditions such as temperature and concentrations of reactants were optimized. A system was assembled consisting of a microcomputer interfaced to an potentiometer and a double walled cell, for thermostatization, using platine electrodes as indicators and Ag/AgCl reference electrode. The reactants were added to cell by means of polyethylene tubes, propelled by a peristaltic pump, and the ascorbic acid injected with a 100 μL micropipette. A 24 factorial research design was established for the investigation of the experimental conditions to be optimized. In this design, the studied variables were the concentrations of reactants potassium bromide, cerium (IV) sulfate, malonic acid and sulfuric acid. Afterwards a study of variation of concentrations for each reactant separately was carried out, establishing in this way the best working concentrations. An investigation was also carried out to find the adequate temperature to obtain the best oscillating pattern characterized by the largest amplitude. An investigation about interfering substances in the oscillating system was carried out after the establishment of the best working conditions. The methodology for the determination of ascorbic acid resulted in a simple procedure, where the experimental system setup can be used for other investigations, and at low cost, since the amount of reactants used is minimal. The method was successfully carried out for the determination of ascorbic acid in pharmaceutical drugs
Neste trabalho, é proposta a determinação de ácido ascórbico em amostras de medicamentos, utilizando-se um sistema potenciométrico, desenvolvido no laboratório que permitiu o estudo de reações oscilantes. Esse método baseia-se na determinação de ácido ascórbico utilizando como princípio o efeito desta substância no padrão de oscilação da reação de Belousov-Zhabotinskii. As condições experimentais como temperatura e concentrações dos reagentes, foram otimizadas. O sistema era constituído de um microcomputador interfaceado a um potenciômetro, e uma cela de parede dupla, para a termostatização, utilizando-se eletrodos de platina como indicador e referência de Ag/AgCl. Os reagentes foram adicionados à cela através de tubos de polietileno, propulsionados por uma bomba peristáltica, e o ácido ascórbico foi injetado com uma micro-pipeta de 100 μL. Um planejamento fatorial 24, onde as concentrações dos reagentes bromato de potássio, sulfato de cério(IV), ácido malônico e ácido sulfúrico foram as variáveis estudadas no planejamento montado para o estudo das condições experimentais a serem otimizadas. Em seguida foi feito um estudo de variação de concentração para cada reagente separadamente, estabelecendo-se as melhores concentrações de trabalho. Foi feito também um estudo da temperatura adequada para se obter o melhor padrão de oscilação caracterizado pela maior amplitude. Após estabelecido as melhores condições de trabalho, foi realizado o estudo de substâncias interferentes no sistema oscilante. A etodologia para a determinação de ácido ascórbico resultou em um procedimento simples, onde a montagem do sistema pode ser reutilizada em outros estudos, e de baixo custo, pois a quantidade de reagentes utilizada é mínima. O método foi aplicado com sucesso para a determinação de ácido ascórbico em medicamentos.

No presente trabalho focalizou-se a atenção nas propriedades de substâncias húmicas, em particular a fração de ácido húmico (AH), o qual foi obtido de duas fontes, sendo uma comercial e outra isolada de sedimentos do Rio Tietê, coletados no reservatório de Barra Bonita (SP). O isolamento do AH do sedimento foi realizado segundo o procedimento proposto pela Sociedade Internacional de Substâncias Húmicas (S.I.S.H.). Ambas amostras foram caracterizadas em paralelo através de análise elementar, absorção molecular no visível (razão E4/E6) e infravermelho e teores de cinzas. As propriedades ácido-base das amostras foram estudadas por titulação potenciométrica, adotando-se o modelo de distribuição de sítios discretos, empregando-se funções de Gran modificadas para tratamento dos dados. Foi possível caracterizar seis classes de grupos tituláveis em força iônica 0,1 (NaCI), com pKa entre 3 e 10. Constatou-se maior contribuição de grupos carboxílicos (grupos titulados com pKa < 7) do que fenólicos e amínicos em ambas amostras. Os resultados foram comparados com os métodos clássicos do acetato de cálcio e barita, assim como por titulação condutométrica. Estudou-se as propriedades de complexação dos AHs com íons Cu2+,Pb2+, Cd2+ e Zn2+ através de titulação potenciométrica com eletrodo íon-seletivo de membrana sólida para o CU2+ e de amálgama para os demais íons. Constatou-se a seguinte ordem de estabilidade para os complexos formados com ambos AHs: log K AH-Cu > log K AH-Pb > log K AH-Cd aproximadamente igual a log K AH-Zn. Quanto a capacidade de complexação (Cc), observou-se que CcPb > CcCu > CcCd aproximadamente igual a CcZn.
The aim of the present work was to study the humic substances, with emphasis to the humic acid (HA) fraction isolated from sediments of the Tietê River, collected at the Barra Bonita reservoir. The extraction of the humic acid was performed according to the procedure proposed by the International Humic Substances Society (I.H.S.S.). A commercial humic acid from Aldrich was studied in parallel. Both HA samples were characterized by elemental analysis, molecular absorption in the visible (E4/E6 ratio) and infrared regions, and ash contents. The acid-base properties of both humic acids were studied by potentiometric titrations, adopting the discrete site distribuition model and the modified Gran functions for data fitting. Six classes of titratable groups were characterized in 0,1 mol.L-1 (NaCI) ionic medium, with pKa values between 3 and 10. The sum of carboxylic groups (titratable groups with pKa < 7) was greater than the sum of aminic and phenolic groups for both humic acids. These results were compared with those provided by classical methods such as baryta adsorption and calcium acetate, as well as condutometric titration. The complexing properties were studied with regard to Cu2+,Pb2+, Cd2+ and Zn2+, by potentiometric titration with solid membrane copper ion-selective electrode and amalgam electrodes for the other ions. The following stability was observed for both HAs complexes: log KHA-Cu > log KHA-Pb > log KHA-Cd approximately equal to log KHA-Zn. With regard the complexing capacity (Cc),the following order was observed: CcPb > CcCu > CcCd approximately equal to CcZn.

Modification chimique de polystyrène greffé sur la surface interne de tubes en polyethylène pour rendre anticoagulante la surface interne de ces tubes employés comme catheter. Fixation de groupes fonctionnels sulfonate et sulfamide d'acide aspartique par liaison covalente en para des cycles benzeniques du polystyrène

The use of ion-selective field-effect transistors (ISFETs) as potentiometric microsensors was investigated. In the first stage, an instrument was designed and built to operate an array of ISFETs. A microcomputer was used for instrument control and acquisition of data.
The second phase of research focussed on the development of a pH sensitive radiotelemetric device that could eventually be used for the noninvasive monitoring of gastric pH. The first attempt used an ISFET as a variable resistor in a simple telemetry circuit. The drift in the pH dependent signal from this device was significant. The use of a differential sensor was studied as a possible way to minimize the effect of signal drift. This system measured the differential output of a pH ISFET and a pH insensitive ISFET. The pH insensitivity was due to an alkanethiol monolayer at the ISFET$ vert$solution interface.
It was shown that ISFETs are well suited for use as sensors in telemetry devices. The union of these previously independent research areas has been achieved.