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Integration of total chemical analysis with microchip capillary electrophoresis

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Title: Integration of total chemical analysis with microchip capillary electrophoresis
Author(s): Railila, Annika
Contributor: University of Helsinki, Faculty of Science, Department of Chemistry
Discipline: Analytical Chemistry
Language: English
Acceptance year: 2013
Total chemical analysis systems (TAS) have been a hot topic during the last 10 years mainly due to the possibilities of analyzing small samples, as small as nanoliters and femtoliters, in a quick manner and requiring only small amounts of buffers. In this thesis the focus is on the studies carried out on microchips that integrate sample pretreatment , capillary electrophoretic (CE) separation and detection steps.. The techniques used have mainly been developed for the analysis of biological samples, such as drugs, proteins and biomarkers, and for DNA profiling. On-line sample pretreatments include preconcentration, sample cleanup and derivatisation, all with the aim to minimise sample losses and the effective analysis time. By preconcentrating the analytes on-line the detection limits can be decreased and the analyte detection responses increased and band broadening is avoided. In addition, TAS devices allow portable and in-situ analyses. making the systems useful especially in environmental studies, and in forensic and medical science. The experimental part of the thesis was focused on the physico-chemical characterization of some phosphonium-based ionic liquids. The specific aim was to get a further insight into phosphonium-based ionic liquids (ILs) used in electrokinetic chromatography (EKC) as psedostationary phases. The critical micelle concentration (CMC) values for the ILs were determined for the calculation of the distribution constantsfor the model analytes. Another purpose of the work was to investigate the ionicity of some phosphonium-based ILs that is of great importance of understanding the solvent properties and vapor pressures of the ILs. In order to calculate the ionicity, the temperature-dependent conductivity is needed along with the viscosity. Therefore the temperature-dependent conductivity of some ILs was studied. The CMCs determined by the CE method was 0.50 mM for [P14444]Cl and 0.68 mM for [P14444]OAc. The measurements were done in the same way in both cases and the electropherograms looked very similar. The water-soluble phosphonium-based ILs studied in this work seemed to have a linear temperature dependent conductivity when diluted with water. In contrast, the concentrated ILs had a much lower conductivity and the temperature dependency was of a polynomial form.

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