Identificador: TDX:796
Autores: Puig Guiral, Patricia
Resumen:
The thesis entitled 'Combination of preconcentration techniques with capillary electrophoresis for determining beta-lactam antibiotics' has been focused in the development of several strategies for improving sensitivity in capillary electrophoresis. These strategies have been applied for determining beta-lactam antibiotics in different matrices. <br/><br/>beta-Lactam antibiotics are a family of drug compounds widely used in human and veterinary medicine with therapeutic and prophylactic aims. Moreover, in veterinary medicine they have been used as growth promotors. However, abusive and inappropriate use of antibiotics has led to unexpected problems. On the one hand, they are thought to be responsible for the appearance of bacterial strains that are resistant to antibiotics. As a result, antibiotics can not treat infections efficiently. On the second hand, the presence of antibiotics in the food chain can lead to allergic reactions in certain patients. Therefore, it is important to control their presence in different samples.<br/><br/>Capillary electrophoresis (CE) is a good strategy for the determination of these antibiotics due to its high efficiency, resolution and separation power. Moreover, the amount of reagents, organic solvents and sample needed are really small which makes this technique in a cheap and green one. However, CE presents an important drawback, it lacks sensitivity when low concentration levels are needed. To solve this, in the thesis, several strategies have been studied in order to preconcentrate the analytes and then increase their concentration prior to the electrophoretic separation.<br/><br/>Among the different options for preconcentrating analytes it is important to emphasize the electrophoretic-based and the chromatographic-based techniques. The first ones are based on the principle of focusing the analytes according to their different velocities in two separate zones inside the capillary. Of the chromatographic techniques, solid-phase extraction (SPE) is the most important and allows a large sample volume with low concentration to be converted into a low sample volume with higher concentration.<br/><br/>Both, electrophoretic and chromatographic-based techniques have been applied in this thesis for improving sensitivity. Regarding to the application of the firsts ones, different separation modes were studied. When the chromatographic preconcentration was used, the studies differ in how they combine SPE and CE. <br/><br/>In this way different preconcentration techniques have been evaluated by capillary zone electrophoresis (CZE) and micellar and microemulsion electrokinetic chromatography (MEKC, MEEKC). In all the cases, a large sample volume has been introduced into the capillary and then, the sample matrix has been removed in a way that the detection limits decreased.<br/><br/>As far as chromatographic preconcentration is concerned, the combinations studied between SPE and CE were: off-line, in-line and on-line. Unlike when the electrophoretic preconcentration is used, by using the chromatographic-based one, the sample preconcentration usually involves a sample clean-up. So, it allows the analysis of real samples like river water, hospital sewage water or even biological matrices like cow plasma. Detection limits considerably decreased so, a great improvement in sensitivity has been achieved. Finally, in order to increase even further the sensitivity in CE, the combination of electrophoretic and chromatographic techniques has been studied.
Repositori URV