Tesi sul tema "Titration"

The aim of this work was to design a set of rules for levodopa infusion dose adjustment in Parkinson’s disease based on a simulation experiments. Using this simulator, optimal infusions dose in different conditions were calculated. There are seven conditions (-3 to +3)appearing in a rating scale for Parkinson’s disease patients. By finding mean of the differences between conditions and optimal dose, two sets of rules were designed. The set of rules was optimized by several testing. Usefulness for optimizing the titration procedure of new infusion patients based on rule-based reasoning was investigated. Results show that both of the number of the steps and the errors for finding optimal dose was shorten by new rules. At last, the dose predicted with new rules well on each single occasion of majority of patients in simulation experiments.

This diploma thesis dealt with the study of interactions of soil organic matter, specifically humic acids with a pollutant, where the surfactant Septonex was used. Humic acids were isolated from two different soils in the work, namely black earth and cambium. The theoretical part describes the formation of humic acids as such, their possible interactions with substances and the characterization of surfactants. The experimental part is devoted to the characteristics of humic acids using elemental analysis, thermogravimetry and then the most important part of the thesis, namely the monitoring of interactions using isothermal titration calorimetry. The experiment showed that the sample of isolated black earth at the surfactant concentration of 0,075 moldm3 had the best interaction with the surfactant.

Turkey hemorrhagic enteritis virus (THEV) is responsible for the hemorrhagic enteritis (HE) disease in commercial turkeys through infections by its virulent strains. HE is an acute condition characterized by depression, immunosuppression, bloody droppings, intestinal hemorrhage, and death. THEV (also known as turkey adenovirus 3) is an official member of the family Adenoviridae, genus Siadenovirus, species Turkey siadenovirus A. Two main types of live vaccines are currently used for the protection of turkeys against HE; a crude splenic vaccine propagated in live turkeys, and a cell culture-based vaccine generated in RP19 cells. The only laboratory-adapted tests for assessing the titers of these vaccines are agar gel immunodiffusion test and cell culture endpoint dilution, respectively. The assays suffer from low sensitivity, inaccuracy, and time consumption. A SYBR Green-based real time PCR assay for determining the genomic titer of THEV through the quantification of its hexon gene was developed. The assay was applied as a quality control for the titration of splenic vaccines and was found useful in distinguishing the differences in virus titer among many vaccine batches. Additionally, using the qPCR assay along with a cell culture system, a novel infectivity assay was developed for the titration of THEV, as an alternative for the endpoint dilution assay. Applying the assay on nine batches of commercial HE cell culture vaccines, high variations in infectious virus titers were detected. The new method is rapid, sensitive, and very accurate. A strong correlation was found between the genomic titer and qPCR infectious titer in HE cell culture vaccines. Moreover, the qPCR infectivity assay proved as an instrumental research tool. It was used to measure the effect of several treatments of RP19 cells on virus infection. The main target cell type for THEV infection and replication is B-lymphocytes, which are represented in vitro by the B lymphoblastoid, RP19 cells. The cellular surface components used by the virus to gain entry into cells are unknown. As an adenovirus, we hypothesized that THEV uses two different molecules on RP19 cells for the attachment and internalization. A recent study has shown that the synthesized THEV fiber knob domain binds to sialyllactose, based on a glycan array analysis. In our studies, the treatment of RP19 cells with neuraminidases and lectins resulted in high reduction of virus entry, which provide a strong evidence of the utilization of cell surface sialic acids as attachment receptor for THEV. Destruction of surface carbohydrates and proteins on RP19 cells also reduced virus entry, indicating that these components are part of the THEV receptor. Using virus overlay protein blot assay, THEV was found to specifically bind to two RP19 surface membrane proteins, most likely, representing primary and secondary receptors for virus entry. Further studies are required to identify these proteins and verify their role in THEV endocytosis in host cells.
Ph. D.

L’objectif de cette thèse est d’étudier les interactions entre polyélectrolytes (PE) de charges opposées par analyse frontale continue en électrophorèse capillaire (FACCE) et par titration calorimétrique isotherme (ITC), en fonction de la force ionique du milieu et des paramètres physico-chimiques relatifs aux deux partenaires (taux de charge chimique, masse molaire, ramification). Un copolymère statistique d’acrylamide et de 2-acrylamido-2-méthyl-propane sulfonate (PAMAMPS) de taux de charge variant entre 15% et 100% a été synthétisé et caractérisé pour cette étude. En tant que polycation modèle, la poly(L-lysine) a été retenue, sous sa forme linéaire (PLL) ou ramifiée / hyperbranchée (DGL). Des mesures par turbidimétrie ont permis d’étudier la stabilité des complexes de polyélectrolytes (PEC) en fonction de la force ionique du milieu. La détermination de la stœchiométrie des PEC par 1H-RMN a permis d’établir une règle générale pour prédire les stœchiométries de charge des PEC. Les paramètres thermodynamiques d’interactions (constantes et stœchiométries d’interaction, contribution entropique et enthalpique) ont été déterminés, par le tracé systématique des isothermes d’adsorption, en considérant le modèle d’interactions des sites indépendants de même énergie. Une dépendance linéaire entre le logarithme des constantes d’interactions et le logarithme de la force ionique a été observée. Cette dépendance en force ionique confirme le caractère entropique des interactions entre PE de charges opposées. Elle permet aussi de quantifier le nombre de contre-ions relargués lors de la formation du PEC. Cette quantité de contre-ions libérés a pu être comparée à la quantité totale de contre-ions condensés. Cette modélisation permet, en outre, de prédire les constantes d’interaction pour des taux de charge intermédiaires et à différentes forces ioniques
The aim of this thesis is to study the interactions between oppositely charged polyelectrolytes (PE) by frontal analysis continuous capillary electrophoresis (FACCE) and isothermal titration calorimetry (ITC) as a function of the ionic strength of the medium and the physico-chemical properties related to the two partners (chemical charge density, molar mass, ramification). Statistical copolymers of acrylamide and 2-acrylamido-2-methyl-propane sulfonate (PAMAMPS) with chemical charge densities varying between 15% and 100% were synthesized and characterized for this study. Poly(L-lysine) under their linear (PLL) or ramified/hyperbranched (DGL) forms were used as model polycations. Turbidity measurements allowed the study of the stability of the polyelectrolyte complexes (PEC) as a function of the ionic strength of the medium. PEC charge stoichiometries were measured by 1H-NMR, and a general predictive rule that estimates the PEC charge stoichiometry was enounced. The thermodynamic binding parameters (binding constant, stoichiometry, enthalpic and entropic contributions) were determined, by systematically plotting the isotherms of adsorption, and using the model of independent and identical interacting sites. A linear dependence between the logarithm of the binding constants and the logarithm of the ionic strength was observed. This linear dependence confirmed the entropic character of the interactions between oppositely charged PE and allowed quantifying the number of released counter-ions that were compared to the total number of condensed counter-ions. Furthermore, this modelling allowed predicting the binding constants for intermediate chemical charge densities and at different ionic strengths

La digestion anaérobie est un des piliers de l'économie circulaire européenne, produisant du méthane et des engrais organiques à partir de déchets. Le développement de ce secteur passe par la co-digestion et l’optimisation de l'alimentation des procédés. Cela nécessite l'estimation de l'état biologique du digesteur, la caractérisation du substrat ainsi que l’utilisation de modèles prédictifs simulant les performances du digesteur, pour lesquels les solutions actuelles ne sont pas adaptées. Dans cette thèse, un capteur titrimétrique couplant pH et conductivité électrique pour l'estimation des concentrations en acides gras volatils, carbone inorganique et azote ammoniacale a été conçu, améliorant la précision d'estimation des acides gras volatils de 14,5 par rapport aux capteurs actuels. Couplé à l’analyse du biogaz, il permet d'estimer l'état biologique du procédé. En parallèle, une analyse spectroscopique proche-infrarouge, estimant les teneurs en glucides, protéines, lipides, demande chimique en oxygène, rendement et cinétique de production de méthane a été développée réduisant le temps de caractérisation des substrats à quelques minutes. La caractérisation rapide des substrats est utilisée pour implémenter le modèle de digestion anaérobie ADM1 de l’IWA qui prédit les performances d'un digesteur dans des conditions de digestion optimales. Le couplage de l’estimation de l'état biologique à cette approche permet de corriger la prédiction en prenant en compte l'état actuel du digesteur. Cette approche fournit un outil prédictif puissant pour le contrôle avancé des unités de digestion anaérobie ainsi que l'optimisation de la recette d'alimentation
Anaerobic digestion is an important pillar of the European circular economy, producing methane and organic fertilizers from waste. The development of the anaerobic digestion sector goes through co-digestion and feeding strategy optimization. Its development requires the biological state estimation of the plant, substrate characterization and predictive models simulating the plant performances, for which current solutions are not suitable. In this thesis, a titration sensor coupling pH and electrical conductivity for the estimation of volatile fatty acids, inorganic carbon and ammonia has been designed, improving the accuracy on volatile fatty acids estimation by 14.5 compared to current sensors. Along with biogas analyses, it allows estimating the biological state of the unit. Besides, fast near infrared spectroscopic analysis, estimating in a matter of minute carbohydrate, protein and lipid contents, chemical oxygen demand, methane production yield and kinetics, has been developed. Thus fast substrate characterization is then used to implement a modified Anaerobic Digestion Model n°1 which predicts the performances of a plant under optimal condition. Coupling biological state estimation to this approach enables to correct the prediction with the current state of the plant. This approach provides a powerful predictive tool for advanced control of anaerobic digestion plants and feeding strategy optimization

Ions play pivotal roles both biologically and environmentally. The effects felt from the impact of ions, much like their relative charge, can be positive or negative. Ions are responsible for catalyzing and executing precise control over many of the essential processes that occur in our bodies. Ions can also be major contributors as environmental pollutants having catastrophic effects. There is a great deal of interest in better understanding the role and effect of ions in the surrounding environments. The ability to study ions of interest relies on efficient recognition and sensing of these targets. The field of supramolecular chemistry is particularly well suited for this task as it utilizes non-covalent molecular interactions in much the same way natural system involving ions operate. Broadly, this body of research seeks to explore the subtle interactions of various targeted ions with supramolecular receptors. This research is an effort to further understand the nature of these interactions for potential recognition and sensing applications as well as better understanding the highly complex systems found in biology. Chapter I provides a brief overview of various mechanisms of ion coordination in supramolecular chemistry and emphasizes some key examples demonstrating the importance of the various types of coordination as it pertains to the research presented herein. Chapter II highlights a unique class of phosphine oxide-based tripodal ditopic receptors and presents studies on their interactions with alkali metals and halides. Chapter III covers the synthesis and study of anionic binding trends for a series of heteroaromatic-containing urea-based receptors and discusses the influence of anion binding on receptor conformation. Chapter IV provides preliminary results on the application of the bipyridal bisurea-based anion receptor, presented in Chapter III, as ligand for metal salts. Chapter V focuses on a series of pyridal bisurea-based receptors with regard to their ability to serve as chloride sensitive probes in cellular environments. This dissertation contains both previously published and unpublished co-authored material.
10000-01-01

The (α, α, α, α)-5,10,15,20-tetrakis(2-(4-fluorophenylurea)phenyl)porphyrin binds strongly (K(M-1)>104) to the chloride anion and close to 2-3 orders of magnitude less to the acetate anion, in DMSO-d6 as revealed by 1H NMR titration studies. However, the acetate anion showed stronger binding than the chloride anion when ITC analyses were done. Thus, the binding studies' results vary with the use of instrumental method. Other significant differences and similarities observed in the behavior of anion binding with the porphyrin receptor when using the two probes will also be addressed in this report.
Thesis (M.S.)--Wichita State University, College of Liberal Arts and Sciences, Dept. of Chemistry

The effective degree of micellar dissociation of cetyltrimethylammonium bromide (CTAB) micelles has been determined from electrochemical (EMF) measurements using a CTAB selective electrode. Thermodynamic parameters have been determined using the `Ion binding model' and show dominance of hydrophobic interactions in free CTAB micellization. The enthalpy contribution is insignificant. The binding of the surfactant CTAB onto the neutral watersoluble hydrophobic polymers: poly(propylene oxide) (PPO), poly(vinylmethylether) (PVME) and ethyl(hydroxyethyl) cellulose (EHEC) has also been investigated by the EMF technique. In all cases it has been shown that the surfactant binds to the polymer and the bound surfactant exists in the form of small aggregates. The EMF data has been used to investigate the characterization of the binding process. The formation of inclusion complexes between alkylpyridinium bromide (CPyBr) and alkyltrimethylammonium bromide (CIITAB) with a- and ß-cyclodextrins (CDs) have also been investigated by the EMF technique. In addition the thermodynamics of the inclusion on a- and ß-CDs by the surfactants : CTAB, CPyBr, alkylsulfates (COSO3Na) , and alkanesulfonates (CnSO3Na) have been carried out using an Omega isothermal titration calorimeter (ITC). Whereas ß-CD systems form predominantly 1: 1 complexes, a-CD form 1: 1 and a 2: 1 complexes with surfactants having long hydrophobic tails. For both a- and ß-CD the complexation constants increase as the chain length of the surfactant increases, showing that the driving force dominating the formation of these complexes is the hydrophobic effect. The 1: 1 ß- CD/surfactant complexation is accompanied by large increase in entropy. The 1: 1 a-CD/surfactant complexation and all 2: 1 complexation are accompanied by a large increase in enthalpy.

In this thesis, on the basis of the asymmetrical charge distribution of E. coli topoisomerase I, I developed a new rapid procedure to purify E. coli DNA topoismoerase I in the milligram range. The new procedure includes using both cation- and anion-exchange columns, i.e., SP-sepharose FF and Q-sepharose FF columns. E. coli topoisomerase I purified here is free of nuclease contamination. The kinetic constants of the DNA relaxation reaction of E. coli DNA topoisomerase I were determined as well. I also used isothermal titration calorimetry to investigate the energetics of DNA supercoiling by using the unwinding properties of DNA intercalators, ethidium and daunomycin. After comparing the enthalpy changes of these DNA intercalators binding to supercoiled and nicked or relaxed plasmid DNA pXXZ06, I determined the DNA supercoiling enthalpy is about 12 kcal/mol per turn of DNA supercoil, which is in good agreement with the previously published results.

The purpose of this Master's Project was to develop an Acid-Base Titration Simulator. It was also to be a part of the California State University - San Bernardino's GTSS, Generic Tutorial System for the Sciences, project. The main benefit is that students will be able to conduct titration experiments over the Internet without being in the laboratory and without costly equipment or dangerous chemicals. Instructors at the high school and college level can demonstrate the key principles of titration.

Synthesis and ion binding properties of cyclic homopeptides Starting from the isolation of the antibiotic Gramicidin S, the first biologically active cyclopeptide identified in 1944, cyclic peptides have attracted increasing interest due to their unique chemical and biological properties. In cyclic peptides the amino acidic chains are closed in the ring to give structures with reduced conformational freedom compared to linear precursors. As a consequence, cyclic peptides generally have greater resistance to in vivo enzymatic degradation, greater bioavailability and ultimately greater binding affinity and selectivity toward substrates. Synthesis of cyclic peptides, in particular head-to-tail cyclisation, represents a significant synthetic challenge and cyclization reaction requires particular conditions. For instance, high dilution is still the main route applicable to minimize unwanted intermolecular processes. The success or failure of macrocyclization relies on the ability of a linear precursor to conformationally pre-organize its reactive ends bringing them close to each other before ring closure. Many features have been found to favor cyclization such as introduction of cis-amide bond in the middle of the peptide chain, the presence of both D- and L- residues in the termini, introduction of N-methyl amino acids etc. In this thesis the synthesis of a series of linear homopeptides containing lysine, serine and aminoalanine were performed in solution following a classical orthogonal protection scheme. Macrocyclization reactions were carried out on completely protected peptide precursors under high dilution conditions in the presence of different salts (NaCl, LiCl, NaTPB and TEACl) to promote the head-to-tail condensation. Microcalorimetric titrations using linear tetra-, penta- and hexalysine containing peptides as ligands and NaClO4 and TEACl as salts indicated a very weak binding of the peptides with Na+ and a strong binding with Cl-. The binding constants for the complexation of chloride ions were evaluated to be Log K=1.51, Log K=1.47 and Log K=1.68, for tetra-, penta- and hexapeptide, respectively. These findings suggest that the mechanism commonly accepted for the metal-ion assisted cyclization has to be revised indicating that coordination of chloride ions (and not alkali metals) with amide groups along the chain is the factor that predominantly brings N- and C-termini closer, forcing them to react. Accordingly, the highest cyclization yields were obtained when TEACl was used as the salt. Moreover, MD simulations show the formation of stable complexes of linear peptides with Cl- while in complexes with sodium dissociation of the cation occurs. Binding properties of cyclic pentalysine toward different anions were investigated by means of microcalorimetric titrations in CH3CN. In complexation reactions with halides (Cl-, Br-, I-) as well as with NO3-, inflection was observed at a ratio n(A-)/n(L) ≈ 1 which indicates that the stoichiometry of the resulting complex is 1:1. In contrast, with H2PO4- we observed inflection at the ratio n(L)/n(A-) ≈ 2 i.e. two ligands are needed to coordinate one H2PO4- anion. Calorimetric titrations showed also that the most efficient binding of cyclopentalysine is with Cl- with the binding constant of Log K=5.72 while that of cyclohexalysine is with OAc- (Log K > 4, obtained by NMR titrations). In general, cyclic pentapeptide binds stronger all investigated anions than the corresponding cyclic hexapeptide. Complexation reactions of cyclic penta- and hexalysine were also investigated by 1H NMR and ESI-MS titrations. The results are in agreement with those obtained by microcalorimetric titrations. Linear H2N-(Leu)5-COOH and H2N-Phe-Leu-Leu-Phe-Leu-Leu-COOH were also prepared in order to confirm the role of chloride anion in assisting macrocyclization of peptides. With the ultimate goal to prepare a novel class of anion receptors, namely calixarene homo-cyclopeptide derivatives, work is in progress to set-up a simple and efficient method to directly conjugate the prepared homocyclopeptides to calixarenes by exploiting side chain functional groups.

The actual life of a transformer is determined by ageing of the cellulosic insulation such as transformer paper. The presence of moisture in the insulation system decreases the electrical strength of paper and accelerates the aging. It is an efficient way to monitor the moisture content in paper insulation by measuring the dielectric constant of the paper. The moisture dependent permittivity of impregnated transformer paper below 1 MHz has been widely investigated. High frequency (> 1 MHz) dielectric spectroscopy is under requirement since the loss peak information is missing. The impregnated paper is kept in desiccators with saturated salt solutions to get the samples with moisture content from 1 % to 5.5 %. Then they are placed in a coaxial line and the scattering parameters are obtained by modern Vector Network Analyzer. Full wave analysis is utilized to calculate the permittivity from the obtained S-parameters due to its high accuracy. The magnitude of the dielectric spectroscopy below 100 Hz is very dependent on the moisture content while there is a horizontal shift of curves towards higher frequencies depending on the water content over a wide frequency range. The loss peaks appear between 1 MHz and 1 GHz for the impregnated paper with moisture level less than 5.5 %. Due to the limited system accuracy, there is a blank frequency band from 1 MHz to 100 MHz.

The preparation of layered double hydroxides via titration with sodium hydroxide was thoroughly investigated for a number of M(II)/M(III) combinations. These titration curves were examined and used to calculate nominal solubility product constants and other thermodynamic quantities for the various LDH chloride systems.

This thesis describes the use of metals to simultaneously catalyse and template large molecules into a mechanically interlocked system. This mechanical interlocking results in unique properties but is difficult to achieve. In this thesis, techniques to create this mechanical interlocking are developed and improved upon both in solution and on surfaces. In addition, the complex molecules that are created display unique properties and this behaviour is analysed in depth.

Une étude récente sur le transfert peptidique pH dépendant effectuée avec divers ARNt aminoacyles a révélé la dépendance au pH du transfert peptidique. L’instabilité hydrolytique rend impossible l’obtention de la valeur expérimentale du pKa de l’eau donné pour le groupement α-amino des esters 3'-aminoacyladenosine. Comme les analogues de la puromycine sont les analogues les plus proches du 3’-terminal des ARNt aminoacyles et qu’ils contiennent une liaison amide stable en position 3’, il est intéressant de déterminer la valeur du pKa du groupement α-amino de différents analogues de la puromycine mais aussi de corréler ces valeurs de pKa aux valeurs de pKa des groupements ARNt aminoacyles correspondants obtenues par le transfert peptidique pH dépendant. Le premier chapitre de la thèse se concentre sur la synthèse de différents analogues de la puromycine et sur la détermination de leur basicité par une analyse RMN pH dépendante. Ce chapitre discutera aussi la conformation intrinsèque des analogues de la puromycine mesurée par la pH dépendance de leur constante de couplage J1’-2’. Les synthèses d’analogues dinucléotidiques, d’un analogue xylo-puromycine et d’un analogue de désoxyxylopuromycine seront aussi décrites. Les conjugués peptidyl-ARN miment des fragments importants d’intermédiaires de la transduction. Ces analogues peuvent être utilisés comme outils expérimentaux pour comprendre l’évolution de la synthèse codée des peptides. L’innovation dans le concept de ‘négoce moleculaire’ entre les peptides, les oligonucléotides et les bicouches lipidiques, qui pourrait être à la base de l’évolution de la synthèse peptidique contrôlée par l’ARN, nous a poussé à synthétiser des conjugués peptidyl-ARN amphiphiliques et à étudier leurs interactions avec les bicouches lipidiques. Dans le deuxième chapitre les stratégies de synthèse sur support solide utilisant des analogues de puromycine comme élément constitutif seront discutées
A recent pH dependent peptidyl transfer assay in the ribosome with various aminoacyl tRNAs revealed the pH dependence of the peptidyl transfer. Hydrolytic instability makes impossible to obtain the experimental bulk water pKa data for the α-amino groups of 3'-aminoacyladenosine esters. Since puromycin analogues are the most similar analogues of the 3’-end of the aminoacyl tRNAs and they contain a stable amide bond in 3’-position, the determination of the pKa value of the α-amino groups of different puromycin analogues and correlation of these pKa values with those of α-amino groups of the corresponding aminoacyl tRNAs obtained by pH dependent peptidyl transfer deserves attention. Chapter 1 of the thesis focuses on the synthesis of different puromycin analogues and on the determination of their basicities by a pH dependent NMR analysis. This chapter also analyses the intrinsic conformations accessed by the puromycin analogues, as measured by the pH dependence of their J1’-2’ coupling constants. The synthesis of dinucleotide analogues, a xylo-puromycin analogue and a deoxyxylopuromycin analogue will also be described. Peptidyl-RNA conjugates mimic important fragments of natural intermediates of translation. These analogues can be used as an experimental tool to understand the evolution of the coded synthesis of peptides. The novelty in the concept of a ‘molecular deal’ between peptides, oligonucleotides and lipidic bilayers, which may be the basis for the evolution of RNA controlled peptide synthesis, prompted us to synthesize amphiphilic peptidyl-RNA conjugates and to study their interactions with lipidic bilayers. In chapter 2 the solid support synthetic strategies using puromycin analogues as the building blocks will be discussed

In a single Isothermal Titration Calorimetry (ITC) experiment, the Gibbs free energy (∆G), the enthalpy (∆H), entropy (∆S), specific heat capacity (ΔCp) and stoichiometry of binding (n) can be identified. Non-sigmoidal binding isotherms are particularly difficult to interpret, yet these are routinely found in ITC studies. ITC binding studies at 25 °C between tannins and bovine serum albumin (BSA) produced biphasic binding isotherms that were suggested to be indicators of positive cooperative binding. However, reducing the temperature to 10 °C produced monophasic binding isotherms, which raised questions regarding the validity of these binding isotherms being classified as positively cooperative binding. The biphasic binding isotherm had two separate temperature dependences, with the initial stage producing a positive ΔCp and the second stage a negative one. Subsequently, this binding isotherm was suggested to essentially be a composite of two crosslinking events. This idea of two different crosslinking events rather than positive cooperativity was supported by an ITC study on a phytate-lysozyme interaction. The ITC study showed that n became lower with decreasing temperature suggesting a crosslinking process became more extensive. Consequently, phytate may be less able to impair protein bioavailability at lower temperatures. Continuous Isothermal Titration Calorimetry (cITC) is a technique based on a continuous slow injection of titrant. The cITC binding isotherms obtained from the lysozyme-phytate interaction indicated that positive binding cooperativity was not occurring. To determine how phytate can be transported around the blood, an ITC study was performed using phytate and BSA in phosphate buffered saline pH 7.4. No binding was detected meaning that BSA does not transport phytate around the blood. However, in 10 mM ammonium acetate at pH 4 binding between BSA and phytate occurred. Conclusively, this reinforces earlier work that binding assays should be done in physiological conditions otherwise findings could be spurious.

O estudo da variação da composição atmosférica contribui para a compreensão dos efeitos das emissões antrópicas sobre a troposfera. A análise química da água de chuva assume importância neste contexto, uma vez que a precipitação úmida constitui um excelente meio de remoção de muitos poluentes da atmosfera. O aumento de acidez das chuvas, em várias partes do planeta, tem sido associado, predominantemente, à presença de ácidos fortes como o sulfúrico e nítrico, e ácidos orgânicos como acético e fórmico, originados pela oxidação de compostos de enxofre, nitrogênio e carbono, respectivamente. Dando continuidade a pesquisas anteriores sobre deposição úmida realizadas no IQ-USP, no presente trabalho buscou-se extrair mais informações de titulações potenciométricas e condutométricas de água de chuva, mediante aperfeiçoamento dos métodos de cálculo, com recursos quimiométricos modernos, de modo a complementar as medidas de pH e condutividade convencionais. As concentrações de espécies ácidas ou básicas nas amostras de água de chuva são da ordem de 10-5 mol L-1, muito abaixo das concentrações empregadas na prática cotidiana das titulações potenciométricas (tipicamente, no intervalo de 10-1 a 10-3 mol L-1). Dessa forma, propôs-se o uso de um método de regressão não linear (RNL) multiparamétrica, baseado no método de Levenberg-Marquardt, para a análise de dados potenciométricos (TP-RNL) após procedimento de transposição de coordenadas das curvas de titulação. Ao lado das determinações das concentrações dos analitos, pôde-se estimar ou refinar as constantes de protonação das bases de Brönsted presentes. Para tanto, procedeu-se ao ajuste por RNL das concentrações e/ou das constantes de protonação das bases presentes, de modo a minimizar o quadrado dos desvios entre os valores experimentais e os calculados em função do titulante adicionado, recorrendo a uma equação geral baseada no número médio de protonação de cada uma das bases. Ficou demonstrada a possibilidade de se determinar a soma de ácidos fortes completamente dissociados, soma de ácidos fracos com pK próximo a 4 (principalmente ácidos acético e fórmico), HCO3-/H2CO3 e a soma de bases fracas com pK ao redor de 9 (essencialmente NH3/NH4+). Durante as titulações, a facilidade em se coletar medidas de condutância simultaneamente às de pH levou a elaboração de um método sofisticado de análise de curvas de titulação condutométrica. Para tanto, desenvolveu-se uma equação de RNL baseada na contribuição das espécies em cada valor de pH e na condutância iônica medida (TC-RNL). A equação de TC-RNL é alimentada por dados de pH em função do titulante adicionado, oriundos de titulações potenciométricas. Dessa forma, foi possível caracterizar diretamente amônio e bicarbonato, além do conteúdo iônico total que não participa dos equilíbrios ácidos/base existentes no sistema. Adicionalmente, foi possível separar a contribuição do ácido acético da do fórmico, tarefa impossível por TP-RNL, ao menos nas baixas concentrações encontradas na chuva. Nas mesmas amostras de chuva tituladas foi procedida a análise por eletroforese capilar de zona com detecção condutométrica sem contato (CZE-CCD), conforme procedimento descrito na literatura, estimando-se os cátions e ânions majoritários. Num aperfeiçoamento do método para ânions, viabilizou-se a determinação simultânea HCO3-. Para validar os resultados obtidos por CZE-CCD, recorreu-se à cromatografia de íons. As concentrações de vários analitos, dependendo das amostras de chuva, avizinham-se do limite de quantificação das técnicas TP-RNL, TC-RNL e CZE-CCD. Mesmo assim, para as amostras de chuva analisadas, em geral, houve concordância satisfatória entre os valores estimados pelas três técnicas para espécies agrupadas da seguinte forma: ácidos fortes, ácidos fracos, amônio e bicarbonato.
Ivestigation of the variability of atmospheric chemical composition is an important tool for the evaluation and comprehension of anthropic emissions effects.Rainwater analysis has great importance in this context because wet deposition represents an efficient removal route of many atmospheric pollutants. The acidification of rainwater over wide regions of the planet is associated with the increased presence of strong acids, like sulfuric and nitric ones, and organic acids, such as acetic and formic, mainly originated from oxidative reactions od sulfur, nitrogen and carbon compounds in the atmosphere. In the context of a broad research line at IQ-USP devoted to the study of wet deposition and associated atmospheric chemistry, this dissertation advances the subject of using moderm chemometric methods to extract reliable analytical information from potentiometric and conductometric titrations of rainwater. The concentrations of acidic and alkaline species in rainwater are typically below 5 x 10-5 mol L-1, out of the reach of conventional potentiometric titrations (widely applied in the range of 10-1 and 10-3 mol L-1). Thus, multiparametric non-linear regression based on Levenberg-Marquardt method combined with coordinates transposition to reduce iterative calculation is proposed for the analysis of potentiometric data (PT-NLR). General equations based on the average protonation number of each base are used to describe the system. Bases concentrations and/or protonation constants are adjusted by NLR in order to minimize the sum-of-squares of the residuals between experimental and calculated values of the titration curves. The data analysis was tuned to provide four parameters as output: the sum of strong acids, the sum of weak acids with pK around 4.2 (mainly acetic and formic acids), the sum of HCO3-/H2co3 and the sum of weak bases with pK near 9 (essentially NH3/NH4+). To extract more analytical information from the acid/base titrations, conductance meassurements were made simultaneously with the pH readings, and a sophisticated data analysis method was envisioned. The pH data and available protonation constants for bases included in the model are used to compute the distribution of the species. The available conductivity of each species of the model is introduced in a general equation where the only unknowns are the total concentrations of the bases and of electrolyte not involved in acid/base equilibria. All these concentrations are adjusted by NLR on the conductance data, resulting in the first successful conductometric titration method with non-linear regression analysis, CT-NLR. The great advantage over PT-NLR was the capability to distinguish the contributions of acetic and formic acids in rainwater (an impossible task in PT-NLR method), but total strong acids, ammonium and bicarbonate are determined as well, beside the total ionic content of species not involved acid-base equilibria. Rainwater samples were also analysed by capillary zone electriphoresis equipment with contactless conductometric detection (CZE-CCD), as decribed in literature, regarding the major cations and anions. An improved CE method for anions was developed to afford the simultaneous determination of HCO3-. Validation of results was made with the reference method of ion chromatography. Although in many samples some analytes are low and close to the quantification limits od CZE-CCD, PT-NLR and CT-NLR, satisfactory agreement was achieved between values obtained by the three techniques for strong acids, weak acids, ammonium and bicarbonate.

Arbetet har mestadels utförts i kokeriet på Domsjö Fabriker i syfte att kartlägga hur processförhållandena hänger samman med koncentrationen sulfatjoner. Detta för att lättare kunna undvika förhållanden i processen som innebär mycket höga värden. Arbetet ingår i examen för högskoleutbildningen: processoperatör vid Umeå Universitet.Vid Domsjö Fabriker har tidigare liknande mätningar gjorts i kokeriet och det har konstaterats att koncentrationen sulfatjoner hänger samman med pH och tid. Syftet är att djupare kartlägga hur processförhållandena hänger samman för att lättare kunna undvika förhållanden som innebär höga koncentrationer sulfatjoner. Målet med examensarbetet och dess undersökning är att sammanställa resultat som visar hur och när under koket som sulfatjoner bildas i stora mängder i kokeriet. Förfarandet av undersökningen har bestått i att prov tas ut i provserier om fyra provtillfällen per kok, fryses in och slutligen analyseras genom titrering och pH-mätning.Efter totalt 22 stycken provserier om fyra prov från de olika kokarna konstaterades att sulfatkoncentrationen är högst i slutet av nedgasningssteget. Det första provtillfället hade de högsta pH-värdena men också de lägsta koncentrationerna sulfat. Inget av dessa värden sticker ur och anses onormalt på något sätt. Om sulfatkoncentrationen påverkas av pH-värdet går inte att fastställa av detta arbete, då det inte är de lägsta pH-värdena som genererar de högsta sulfatkoncentrationerna utifrån resultatet i undersökningen.
This work has been performed in the digester at Domsjö Fabriker in order to clarify the concentration of sulphate-ions comparing to different driving-conditions in the process. The reason to this is to understand and be able to avoid conditions in the digester process that means very high concentrations of sulphate-ions. The work is included in the examination of higher education: process operator at Umeå University.At Domsjö Fabriker similar studies have been done in the digester and from that it has been found out that the concentration of sulphate-ions is connected to pH and over time. The purpose is to approve the understanding of the process conditions to avoid extremely high concentration of sulphate-ions. The mission with this work and the measurements included in the work is to put together results that show when the concentration of sulphate-ions is high. The procedure of the study has consisted in taking samples in series of four, frozen the samples and finally analyzing them by titration and pH-measurements.After 22 evaluated trial-series á four samples each from the boilers it was concluded that the concentration of sulphate-ions was the greatest in the end of this process-step. The pH was upper and the concentration of sulphate lower in the first sample. None of the data is abnormal in any way, and they are all connected and relevant to each other. In this experiment it is not possible to state if the concentration of sulphate is affected by the pH or not.