<p> Affinity capillary electrophoresis (ACE) is a versatile technique for assessing non-covalent molecular interactions in free solution provided that there are significant changes in apparent analyte mobility as a result of specific complexation. The thermodynamics of receptor binding are vital for controlling the selectivity in molecular recognition, which are dependent on the electrolyte composition of solution. In addition, the conformational properties of the complex (e.g., size, shape) can also contribute a secondary influence on receptor selectivity that has been relatively unexplored in ACE to date. In this study, dynamic 1:1 host-guest inclusion complexation involving a anionic resorcin[4]arene with a group of neutral corticosteroids was examined by ACE, where the macrocycle serves as both an intrinsic buffer and electrokinetic host. The tetraethylsulphonate derivative of 2-methylresorcin[4]arene (TESMR) was first synthesized via an acid-catalyzed condensation reaction, which was then fully characterized in terms of its weak acidity (pKa), mobility, UV spectral and buffer capacity properties. TESMR solutions were demonstrated to have stable intrinsic buffer and ion transport properties at pH 7.5 even at low ionic strength. It was determined that over a 200 % enhancement in the apparent binding constant (KB) was realized by ACE when using TESMR as an intrinsic buffer at pH 7.5 relative to an extrinsic sodium phosphate buffer system, which was also confirmed by 1H-NMR. The coupling of thermodynamic (KB) and electrokinetic (μep, AC) factors associated with complex formation in buffered aqueous solutions that minimize the effects of extrinsic electrolytes serves to enhance enthalpy-driven molecular recognition processes by ACE.</p> / Thesis / Master of Science (MSc)

Yes / Many in-vitro methods for prediction of skin permeability have been reported in literature. Cerasome electrokinetic chromatography is one of the most sophisticated approaches representing a maximum level of similarity to the lipid phase of the stratum corneum. One goal of this study was to investigate the affinity pattern of Cerasome and to compare it with the permeability profile of human skin. Another purpose was to study the applicability of Hansen solubility parameters for modelling skin permeation and to investigate the predictive and explanatory potential of this method. Visualisation in Hansen diagrams revealed very similar profiles of Cerasome electrokinetic chromatography retention factors and skin permeability coefficients. In both cases, the characteristic pattern with two clusters of highly retained or highly permeable substances could be shown to be mainly caused by two groups of compounds, one of them with high affinity to ceramides, fatty acids and lecithin and the other being more affine to cholesterol. If based on a sufficiently comprehensive experimental dataset, model-independent predictions of skin permeability data using three-component Hansen solubility parameters are able to achieve similar accuracy as calculations made with an Abraham linear free energy relationship model in which the compounds are characterized by seven physicochemical descriptors.

Micellar electrokinetic chromatography (MEKC), one of the major capillary electrophoresis (CE) modes, has been interfaced to mass spectrometry (MS) to provide high sensitivity and selectivity for analysis of chiral compounds. The research in this dissertation presents the development of novel polymeric glucopyranoside based molecular micelles (MoMs) (aka. polymeric surfactants) and their application in chiral MEKC-MS. Chapter 1 is a review of chiral CE-MS - in the period 2010-2015. In this chapter, the fundamental of chiral CE and CE-MS is illustrated and the recent developments of chiral selectors and their applications in chiral EKC-MS, CEC-MS and MEKC-MS are discussed in details. Chapter 2 introduces the development of a novel polymeric α-D-glucopyranoside based surfactants, n-alkyl-α-D-glucopyranoside 4,6-hydrogen phosphate, sodium salt. In this chapter, polymeric α-D-glucopyranoside-based surfactants with different chain length and head groups have been successfully synthesized, characterized and applied as compatible chiral selector in MEKC-ESI-MS/MS. or the enantioseparation of ephedrines and β-blockers. Chapter 3 continues to describe the employment of polymeric glucopyranoside based surfactants as chiral selector in MEKC-MS/MS. The polymeric β-D-glucopyranoside based surfactants, containing charged head groups such as n-alkyl β-D-glucopyranoside 4,6-hydrogen phosphate, sodium salt and n-alkyl β-D-glucopyranoside 6-hydrogen sulfate, monosodium salt were able to enantioseparate 21 cationic drugs and 8 binaphthyl atropisomers (BAIs) in MEKC-MS/MS, which promises to open up the possibility of turning an analytical technique into high throughput screening of chiral compounds. Physicochemical properties and enantioseparation capability of polymeric β-D-glucopyranoside based surfactants with different head groups and chain lengths were compared. Moreover, the comparison of polymeric α- and β-D-glucopyranoside 4,6-hydrogen phosphate, sodium salt were further explored with regard to enantioseparations of ephedrine alkaloids and b-blockers. The concept of multiplex chiral MEKC-MS for high throughput quantitation is demonstrated for the first time in scientific literature.

Liquid crystals are widely used in electronics, medicine and other fields. Analytical separations are important in the development of new liquid crystals to control the purity of synthesized substances. The sample analysis is important for detection of impurities formed during synthesis and for determination of chiral purity of the substance. Liquid crystal-forming substances cannot be separated by capillary zone electrophoresis due to the absence of readily ionizable groups. Electrokinetic chromatography is a method in which a suitable surfactant is added to the background electrolyte. The uncharged substances then interact with the electrically charged surfactant to obtain an effective charge. Separation can occur if they interact differently with the added surfactant. Another problem complicating the analysis is the very low solubility of analytes in water. Separations in this work were therefore carried out under non-aqueous conditions in acetonitrile. However, under these conditions a poor repeatability of the migration times of the substances was observed. Therefore, capillaries with differently coated inner walls were used in subsequent measurements. Surface modification should improve the repeatability of migration times. Several types of capillary coating have been tested. Dynamic coating...

Atualmente, as doenças cardiovasculares constituem as principais causas de morte no Brasil e no mundo. As estatinas são consideradas os agentes mais efetivos e mais bem tolerados para o tratamento do aumento excessivo dos níveis de colesterol no sangue, ou hipercolesterolemia. A fluvastatina (FLV), um fármaco hipolipêmico, de segunda geração, pertencente à classe das estatinas, e é comercializada como mistura racêmica, ou seja, uma mistura equimolar da (+)-3R, 5S-FLV e (-)-3S, 5R-FLV. Além disso, é descrito na literatura que o enantiômero (+)- 3R, 5S- FLV possui atividade cerca de trinta vezes maior do que seu antípoda, o que justifica a importância e necessidade de métodos para análise enantiosseletiva de fármacos que possuam um ou mais centros de assimetria. Assim, este trabalho teve como objetivo a extração dos enantiômeros da FLV de matriz biológica (plasma) utilizando uma técnica de eletromigração em capilar, a cromatografia eletrocinética (EKC). A análise da FLV por cromatografia eletrocinética empregou como técnica de concentração online o stacking por injeção de grande volume, em um capilar de sílica fundida não revestido, de 50,0 cm de comprimento efetivo e 75 ?m de diâmetro interno, solução tampão tetraborato de sódio 50 mmol L-1, pH 9,5; adicionado de 20 mmol L-1 de 2-hidroxipropil-?-ciclodextrina como eletrólito de corrida, tensão de +25 kV, temperatura de 15 °C, injeção hidrodinâmica (0,5 psi por 30 segundos) e detecção em 300 nm. A separação dos enantiômeros foi obtida com valores de resolução de 3,0 e eficiência de 255840 e 150056, e tempos de migração de 7,2 e 7,4 minutos para a (+)-3R, 5S- FLV e (-)-3S, 5R- FLV, respectivamente. O procedimento de preparo de amostra foi baseado na extração em fase sólido-líquida (SLE), com a adição de 0,5 mL de solução tampão fosfato de sódio 0,1 mol L-1 pH 7,0 em 0,5 mL de plasma, previamente fortificado com padrão de FLV. A amostra foi aplicada na coluna e depois de 15 minutos, a FLV foi eluída com 4 mL de éter etílico. O método analítico foi validado avaliando os parâmetros seletividade, linearidade, precisão e exatidão inter e intra-dia, limite de quantificação, carry-over, efeito matriz, integridade da diluição e estudos de estabilidade. Além disso, foi realizado o estudo de racemização. Os resultados apresentaram linearidade na faixa de concentração plasmática de 250 a 725 ng mL-1 para cada enantiômero, sendo o limite de quantificação a concentração de 250 ng mL-1. Os estudos de precisão e exatidão apresentaram valores aceitáveis, com variação menor do que 15%. Além disso, não foi observado efeito carry-over e as amostras foram estáveis quando submetidas a ciclos de congelamento e descongelamento, estabilidade de curta e longa duração, pós-processamento e não foi observada racemização dos enantiômeros. Em relação ao efeito matriz, procedimentos alternativos foram usados com sucesso para análise de amostras lipêmicas e hemolisadas de plasmas. Sendo assim, este é o primeiro método bioanalítico desenvolvido, rápido e confiável, para quantificar os enantiômeros da FLV em amostras de plasma por EKC usando a SLE como técnica de preparo de amostra. / Nowadays, cardiovascular diseases are the main causes of death in Brazil and worldwide. Statins are considered the most effective and well tolerated agents for the excessive increase in cholesterol blood levels, or hypercholesterolemia. Fluvastatin (FLV), a hypolipidemic second generation drug belongs to statin drug class, and it is commercialized as a racemate, that is, a equimolar mixture of (+)-3R, 5S- FLV and (-)-3S, 5R- FLV. Moreover, literature describes that (+)-3R, 5S- FLV enantiomer activity is thirty times higher than its antipode, which justifies the importance and necessity of methods for the stereoselective analysis of drugs which possess one or more than one asymmetry centers. Thus, this work aims the extraction of FLV enantiomers from a biological matrix (plasma) using one of the electromigration techniques, the EKC. FLV analysis by EKC employed large volume sample stacking as sample on-column concentration technique using a fused-silica capillary with 50.0 cm effective length and 75 ?m internal diameter, 50 mmol L-1 sodium tetraborate buffer, pH 9,5 plus 20 mmol L-1 2-hydroxipropyl-?-cyclodextrin as a background electrolyte, voltage of +25 kV, temperature of 15ºC, with sample injected in hydrodynamic injection mode (0,5 psi for 30 seconds) and detection using a diode array detector set at 300 nm. The enantiomers resolution was achieved with a resolution value of 3.0, and efficiency of 255840 and 150056, migration times of 7.2 and 7.4 minutes for (+)-3R, 5S- FLV and (-)-3S, 5R- FLV, respectively. Supported liquid extraction was the chosen sample preparation procedure, with the addition of 0.5 mL of 0.1 mol L-1 pH 7.0 phosphate buffer to 0.5 mL of plasma, the mixture was applied to the column and allowed to wet for 15 minutes, 4 mL of ethyl ether was then applied to the top of the column, allowed to percolate by gravity and the eluted solvent was collected in an ambar tube, the solvent was submitted to evaporation under nitrogen flow and the residue was ressuspended for injection in the capillary electrophoresis equipment. The analytical method was validated covering selectivity, linearity, within-run and between-run precision and accuracy, limit of quantification, carry-over, matrix effect, dilution integrity and stability studies parameters. The racemization study was also performed. The results support that the analytical method is linear in the range of concentrations from 250 to 725 ng mL-1for each enantiomer, and the limit of quantification was 250 ng mL-1; the method is precise and accurate, with variation under 15%. Besides, no carry-over effect was observed, and both enantiomers showed to be stable under thaw and freeze cycles, short and long term stability studies, autosampler stability, and also no racemization was observed. Related to matrix effect, alternative procedures were employed sucessfully in case of analysis of lipemeic and hemolized matrices. So, this is the first bioanalytical method developed, fast and reliable, to quantify FLV enantiomers in plasma samples using EKC with SLE as sample preparation procedure.

La propagation sismique dans les milieux poreux est classiquement associée à des phénomènes de dispersion et d’atténuation des ondes sous l’effet des mouvements fluides. Dans certaines conditions, celle-ci peut également être associée à une conversion d’énergie sismique en énergie électromagnétique dite « sismoélectrique ». La théorie des phénomènes sismoélectriques combinant la théorie de l’électrocinétique à la poroélasticité de Biot, repose en grande partie sur les développements de Pride (1994). Sur la base de ces développements théoriques, Pride et Haartsen (1996) relient le champ électrique cosismique à l’accélération sismique qui le génère par une fonction de transfert. Nous proposons une étude quantitative des couplages sismoélectriques en vue de valider la théorie de Pride et sa généralisation en milieu non saturé. Dans ce but, nous avons développé une expérience en laboratoire sur un sable de quartz non-consolidé, menée dans la gamme du kilohertz sur la base d’un dispositif d’acquisition électrique modulable. Deux méthodes de traitement des signaux sont proposées, l’une temporelle, l’autre spectrale, permettant d’obtenir une analyse complète des vitesses de phase, atténuations et fonctions de transfert. Les expériences réalisées se sont focalisées sur l’étude du rôle de la conductivité du fluide et de la saturation en eau dans le phénomène sismoélectrique cosismique. Une étude time-lapse a ainsi pu être réalisée dans des situations de changements de salinité et de teneur en eau. Dans tous les contextes, l’étude quantitative des rapports d’amplitudes des champs sismoélectriques et sismiques E/ü montre une bonne corrélation avec les prédictions théoriques. Par ailleurs, l’étude des variations de saturation dans une gamme allant de la saturation résiduelle en eau (Sw = 0.3) à la saturation totale, montre que: i) les atténuations et fonctions de transfert ont des comportements reliés à la distribution des fluides qui influencent fortement les propriétés mécaniques du milieu ; ii) une inversion de polarité du champ sismoélectrique peut être observée dans le cas très particulier des milieux non consolidés. / Seismic propagation within porous media is usually associated with wave attenuation and dispersion phenomena related to fluid flow. Under certain circumstances, it may also be correlated to a conversion of seismic into electromagnetic energy known as “seismoelectric”. The understanding of seismoelectric phenomena, combining the theory of electrokinetic to Biot’s poroelasticity, relies mainly on the formulation by Pride (1994). On basis of these theoretical developments, Pride and Haartsen (1996) defined a transfer function expressing the link between the coseismic seismoelectric field and the seismic acceleration at its origin. We propose a quantitative analysis of coseismic seismoelectric couplings with the purpose of validating Pride’s theory and generalizing it to partially saturated media. With this aim in view we developed a laboratory experiment involving an adjustable device for electric acquisitions, conducted within the kilohertz range on unconsolidated quartz sand. Experimental data were subsequently processed in both time and frequency domains, enabling a full analysis that embraces phase velocities, attenuations and transfer functions. The conducted experiments focused on the impact of fluid conductivity and water saturation with regard to the coseismic seismoelectric phenomenon. Time-lapse monitoring were accordingly run under varying salinity or water content. In all scenarios, the quantitative analysis of the electric-to-seismic amplitude ratio E/ü appeared in good agreement with theoretical projections. Moreover, investigations of saturation variations, ranging from the residual water saturation (Sw = 0.3) to full saturation, showed that: i) the behavior of attenuations and transfer functions are directly related to fluid distribution, that greatly impacts the mechanical properties of the medium; ii) in the very peculiar case of unconsolidated media, polarity inversion of the coseismic seismoelectric field may be experienced.

Micro- and nano-fluidic devices represent an exciting field with a wide range of possible applications. These devices, typically made of either silica or glass, ionize when placed in contact with water. Upon the application of an electric field parallel to the wall, a flow is produced by the charged walls called the electro-osmotic flow (EOF). Since electric fields are so often used as the driving force in these devices, EOF is an extremely common phenomenon. For this reason it is highly desirable to be able to control EOF in order to optimize the functioning of these devices. One method which is quite common experimentally is the modification of the surface using polymer coatings. These coatings can be either adsorbed or grafted, and charged or neutral. The first part of this thesis looks at the role of neutral adsorbed polymer coatings for the modulation of EOF. Specifically our simulation results show that for adsorbed coatings made from a dilute polymer solution the strongest quenching of EOF is found for an adsorption strength at the phase transition for adsorption of the polymers. Further evidence is presented that shows that by using a high density of polymer solution and a polymer which has a strong attraction to the surface a very thick polymer layer can be created. Next the case of charged grafted polymer coatings is examined. The variation of the EOF with respect to several key parameters which characterize the polymer coating is investigated and compared to theory. The prediction that the electrophoretic velocity of the polymers is the same as the EOF generated by a coating made up of the same polymers is found to be false though the two values are quite close. The last section presents results which show how hydrodynamic interactions in charged polymer systems can be modeled mesoscopically without the use of explicit charges by forcing a slip between monomers and the surrounding fluid. This model is validated by simulating some surprising predictions made in the literature such as an object with no net charge having a non-zero force when subjected to an electric field, and how the velocity can even be perpendicular to the applied electric field. The thesis can be roughly divided into two topics: using polymer coatings to modulate EOF, and the free solution electrophoresis of polyelectrolytes. While EOF and free solution electrophoresis might seem unrelated it will be shown that the concepts are the same in both cases. In fact while not investigated in this thesis, the mesoscopic simulation methods for electrophoresis could be applied to the modulation of EOF with polymer coatings allowing for the simulation of longer length and time scales or more complex systems such as heterogeneously grafted colloids.

Micro- and nano-fluidic devices represent an exciting field with a wide range of possible applications. These devices, typically made of either silica or glass, ionize when placed in contact with water. Upon the application of an electric field parallel to the wall, a flow is produced by the charged walls called the electro-osmotic flow (EOF). Since electric fields are so often used as the driving force in these devices, EOF is an extremely common phenomenon. For this reason it is highly desirable to be able to control EOF in order to optimize the functioning of these devices. One method which is quite common experimentally is the modification of the surface using polymer coatings. These coatings can be either adsorbed or grafted, and charged or neutral. The first part of this thesis looks at the role of neutral adsorbed polymer coatings for the modulation of EOF. Specifically our simulation results show that for adsorbed coatings made from a dilute polymer solution the strongest quenching of EOF is found for an adsorption strength at the phase transition for adsorption of the polymers. Further evidence is presented that shows that by using a high density of polymer solution and a polymer which has a strong attraction to the surface a very thick polymer layer can be created. Next the case of charged grafted polymer coatings is examined. The variation of the EOF with respect to several key parameters which characterize the polymer coating is investigated and compared to theory. The prediction that the electrophoretic velocity of the polymers is the same as the EOF generated by a coating made up of the same polymers is found to be false though the two values are quite close. The last section presents results which show how hydrodynamic interactions in charged polymer systems can be modeled mesoscopically without the use of explicit charges by forcing a slip between monomers and the surrounding fluid. This model is validated by simulating some surprising predictions made in the literature such as an object with no net charge having a non-zero force when subjected to an electric field, and how the velocity can even be perpendicular to the applied electric field. The thesis can be roughly divided into two topics: using polymer coatings to modulate EOF, and the free solution electrophoresis of polyelectrolytes. While EOF and free solution electrophoresis might seem unrelated it will be shown that the concepts are the same in both cases. In fact while not investigated in this thesis, the mesoscopic simulation methods for electrophoresis could be applied to the modulation of EOF with polymer coatings allowing for the simulation of longer length and time scales or more complex systems such as heterogeneously grafted colloids.

Chemically and physically patterned surfaces can be used as templates to guide nano- and micro- scale particle assembly, but the design is often limited by an inability to sufficiently characterize how pattern features influence local particle-surface interactions on the order of thermal energy, kT. The research outlined in this dissertation describes comprehensive optical microscopy (i.e. evanescent wave, video) measurements and analyses of many-body and multi-dimensional interactions, dynamics and structure in inhomogeneous colloidal fluid systems. In particular, I demonstrate how non-intrusive observation of an ensemble of particles diffusing past each other and over a physically patterned surface topography can be used to obtain sensitive images of energy landscape features. I also link diffusing colloidal probe dynamics to energy landscape features, which is important for understanding the temporal imaging process and self-assembly kinetics. A complementary effort in this dissertation investigated the use of external AC electric fields to reversibly tune colloidal interactions to produce metastable ordered configurations. In addition, the electrical impedance spectra associated with colloidal assemblies formed between interfacial microelectrode gaps was measured and consistently modelled using representative equivalent circuits. Significant results from this dissertation include the synergistic use of the very same colloids as both imaging probes and building blocks in feedback controlled selfassembly on patterns. Cycling the AC field frequencies was found to be an effective way to anneal equilibrium colloidal configurations. Quantitative predictions of dominant transport mechanisms as a function of AC electric field amplitude and frequency were able to consistently explain the steady-state colloidal microstructures formed within electrode gaps observed using video microscopy. A functional electrical switch using gold nanoparticles was realized by reversibly forming and breaking colloidal wires between electrode gaps. Extension of the concepts developed in this dissertation suggest a general strategy to engineer the assembly of colloidal particles into ordered materials and controllable devices that provide the basis for numerous emerging technologies (e.g. photonic crystals, nanowires, reconfigurable antennas, biomimetic materials).

The development and characterization of bipolar electrode (BPE) focusing is described. BPE focusing is an electrokinetic equilibrium technique in which charged analytes are focused and locally enriched on an electric field gradient in the presence of a counter-flow. This electric field gradient is formed at the boundary of an ion depletion zone – the direct result of faradaic reactions occurring at the BPE in the presence of an externally applied electric field. Direct measurement of the electric field strength in the ion depletion region shows that the electric field is enhanced in this region and takes on a gradient shape, confirming the results of numerical simulations. Transient electric field measurements with simultaneous monitoring of a focused fluorescent tracer reveal that the field gradient forms rapidly upon application of the external field and remains stable over time with the tracer focused at a local field strength predicted by simple electrokinetic equations. These transient electric field measurements probe the effect of individual experimental parameters on the electric field gradient and the focused band. The results of these studies indicate that a steeper field gradient leads to enhanced concentration enrichment of the analyte. The slope of the gradient is increased with higher concentration of the running buffer and higher applied field strength. The addition of pressure driven flow across the microchannel moves the location of the field gradient and the position of the focused band. Further enhancement of enrichment is achieved through the suppression of Taylor dispersion after coating the microchannel with a non-ionic surfactant. The findings of these studies have motivated the transition of BPE focusing to smaller microchannels. A decrease in microchannel size not only decreases Taylor dispersion, but also provides access to higher buffer concentration and higher applied field strength, both of which enhance enrichment. The result is a three-order-of-magnitude increase in total analyte enrichment at a much higher enrichment rate. Furthermore, a dual channel configuration for BPE focusing is introduced which provides greater control over focusing conditions. Finally, the formation of ion depletion and enrichment zones at a BPE in a microchannel is shown to mimic ion concentration polarization (ICP) at micro-/nano-channel junctions. This is significant because this faradaic ICP provides a model to which traditional ICP can be compared and is achieved in a more easily fabricated device. In summary, the fundamental principles of BPE focusing are described. A greater understanding of the effect of experimental parameters on the focusing process leads to an unprecedented magnitude and rate of enrichment in a simple device architecture. / text