Solid phase extraction is one of the most widely used methods to concentrate diluted compounds in a solution. Substances can be extracted into admicelles and hemimicelles, which are surface adsorbed micelles and surfactant monolayers, respectively. Investigations of the electrical control of surfactants on surfaces for the purpose of analyte preconcentration prior to chromatographic analysis are presented. The surfactant layer serves as the “stationary phase” in a solid phase extraction sorbent scenario. Analytes are adsorbed on this layer, and then released from the solid phase via surfactant removal. The attachment and removal of the surfactant are controlled by means of an electric field. Because the surfactant-analyte association is released by electrical control, organic solvents, which are used in conventional solid phase extraction, are not required. Therefore, this procedure is advantageous for method development and environmental concerns. Presented is the preconcentration of a test probe, 2-naphthol, using electrical control of the formation and release of dodecyl sulfate on planar gold, gold coated stainless steel, and a porous stainless steel frit, using impedance spectroscopy to observe the layer formation with various surfactant concentrations and applied potentials.

The diploma thesis deals with the preparation and characterization of catanionic complexes and their possible application to pharmaceutics and medicine. The catanionic complexes were prepared by mixing two oppositely charged surfactants with the concentration of 20 mmol·dm­3 in various volume ratios. Two systems were analyzed – CTAB + SDS and Septonex + SDS. Both systems were prepared in an aqueous and physiological environment. The turbidimetric analyses provided results of the intensity of turbidity of the prepared mixtures. The size and stability of the prepared particles were determined by DLS and ELS measurements. CTAB-rich samples showed significant viscosity changes and they were therefore characterized by rheological measurements. The results of this work show that the asymmetry of alkyl chains, surfactant selection, temperature, and ionic strength have a significant influence on the properties and self-assembly of surfactants in catanionic complexes.

Orientador: Watson Loh / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-10T12:25:31Z (GMT). No. of bitstreams: 1 Padula_Lilian_M.pdf: 1356647 bytes, checksum: f598e703185d3612f096dbc7d319e2d8 (MD5) Previous issue date: 2007 / Resumo: Polieletrólitos e surfatantes de carga oposta associam-se fortemente, levando à formação de fases líquido cristalinas com estruturas supramoleculares. A geometria da fase líquido cristalina depende de parâmetros tais como: concentração, razão molar (surfatante/ monômero), características do polímero, presença de aditivos e cossolventes. O objetivo desse trabalho é estudar o equilíbrio de fases e mudanças estruturais das fases líquido cristalinas em sistemas binários contendo complexo polietilenoimina-dodecilsulfato - (PEI-DS) e água, observando assim, a dependência das fases em relação às variáveis tais como razão molar surfatante/ monômero, massa molar e estrutura do polímero (ramificado ou linear) e quantidade de água. Os complexos apresentaram diferenças de comportamento quando utilizados polímeros de diferentes massas molares. O polímero de maior massa molar (2000 'g.mol POT. -1') apresentou apenas estruturas lamelares, já o polímero de menor massa molar (423 'g.mol POT. -1') apresentou estruturas lamelares e hexagonais. Depois de estudados os efeitos das diferentes características do polímero sobre o sistema binário composto por complexo e água, foi escolhido um determinado complexo cuja razão molar 'N IND. SURFATANTE'/ 'N IND. MONÔMERO' é 0,75. Este foi estudado na presença de água e um cossolvente. Os cossolventes escolhidos foram decanol e p-xileno, para ambos os sistemas houve predominância de fase hexagonal. De maneira geral, a troca do contra-íon simples, Na+, pelo contra-íon polimérico, PEI, provocou diferenças no comportamento das mesofases tanto na geometria quanto nas dimensões estruturais, tanto para os sistemas binários quanto para os sistemas ternários / Abstract: Polyelectrolytes associate strongly with oppositely charged surfactants in water, being able to generate liquid crystalline phases with interesting supramolecular structures. The geometry of the liquid crystalline phase depends on parameters such as: concentration, surfactant/monomer ratio, polymer characteristics and presence of cosolvents. The objective of this work is to study the phase equilibria and the structural changes of liquid crystalline phases in binary systems which contain a complex polyethyleneimine dodecylsulfate - (PEI-DS) and water, analyzing the dependence of these phases on variables such as surfactant/monomer ratio, polymer molar mass and structure (branched or linear) and water content. Different polymers led to different phase behavior. While complex with PEI 2000 'g.mol POT. -1' formed only lamellar phases the PEI 423 'g.mol POT. -1' formed lamellar and hexagonal ones. The complex formed with surfactant/ monomer ratio of 0.75 was studied in the presence of water and cosolvents. The cosolvents were decanol and p-xylene and for both systems the hexagonal phase predominate. The counterion exchange from simple, Na+, to polymeric, PEI, produced differences on mesophases geometry and structural dimensions, both in binary and ternary systems / Mestrado / Físico-Química / Mestre em Química

In this diploma thesis was studied time-resolved fluorescence in polymer-surfactant system. At first aggregation numbers of cationic (cetyltrimethylammonium bromide), anionic (sodium dodecylsulfate) and nonionic (Triton X-100) surfactants were studied by steady-state and time-resolved fluorescence spectroscopy. These two methods were compared. Aggregation numbers by steady-state method were always lower than aggregation numbers measured by time-resolved method. Steady-state method of determination aggregation numbers is useless for surfactants with high aggregation number and for aerated samples. Addition of hyaluronan to surfactant system was studied. There was observed change in aggregation number after addition of hyaluronan and change in percentage of dynamic quenching after addition of hyaluronan. Hyaluronan affected aggregation number of cetyltrimethylammonium bromide and Triton X-100. Hyaluronan increased percentage of dynamic quenching in cetyltrimethylammonium bromide and in Triton X-100. Pyren in sodium dodecylsulfate was quenched by sphere of action with negligible percentage of dynamic quenching and addition of hyaluronan had no effect on quenching. As next goal of this thesis, the determination of the position of fluorescence probe pyrene in cetyltrimethylammonium bromide, sodium dodecylsulfate and Triton X-100 micelles was chosen. Position of pyrene changed with charge and structure of micelles. Next was studied how percentage of dynamic quenching by iodide compounds changes with different charge of micelle. In all cases majority of dynamic quenching was calculated.