Identificador: TDX:786
Autors: Macià i Puig, Ma Alba
Resum:
The entitled Doctoral Thesis, 'Diferents estratègies per augmentar la sensibilitat en electroforesi capil·lar. Aplicació a la determinació de fàrmacs antiinflamatoris', has been based on the development of different strategies to decrease the limits of detection (LODs) in capillary electrophoresis (CE) to determine anti-inflammatory drugs. The developed strategies have been based on injecting a large volume of sample into the capillary by application electrophoretic and chromatographic preconcentration techniques, and using the mass spectrometry (MS) as the detection system to increase the detection capacity of the analytes. <br/>This Doctoral Thesis has been centred on the determination of nonsteroidal anti-inflammatory drugs (NSAIDs) in the aquatic environment at low concentration levels. In the last years, the interest to determine them has considerably grown due to the high consume in humans and in animals. These drugs arrive in the sewage treatment plants (STPs) by different source, and subsequently these can entry into the aquatic environment due to its high stability. <br/>Different studies have demonstrated the determination of these drugs at low ng·L-1 levels in surface waters. These studies have principally carried out by gas chromatography (GC) and liquid chromatography (HPLC) by using mass spectrometry as the detection system. CE has also been used to determine these drugs, but its principal application has been for the analysis of biological samples. <br/><br/>Although the high advantages that presents the technique, this shows a low sensitivity that overcomes the determination of analytes at low concentration levels. This is a consequence of the low amount of sample that can be injected into the capillary and the small path length. With the aim of improving the sensitivity and extending the CE applicability in others fields, such as the <br/>environmental, then the development of different strategies to decrease the LODs are very important and these are object of studying of different research groups. <br/><br/>In this Doctoral Thesis have been applied and compared different electrophoretic preconcentration techniques to determine these drugs in the different electrophoretic modes, such as capillary zones electrophoresis (CZE), microemulsion electrokinetic capillary chromatography (MEEKC) and micellar electrokinetic capillary chromatography (MEKC). Frequently, in these preconcentration techniques the sample matrix has been removed from the capillary by suppressing the electroosmotic flow (EOF). The advantage of adding an EOF suppressor in the electrophoretic medium is that the preconcentration and the electrophoretic separation can consecutively be performed by applying an only negative voltage. <br/><br/>The application of a chromatographic preconcentration technique, based on the in-line coupling between solid phase extraction (SPE) and CE, has also been applied to determine NSAIDs in water samples. The high potential of the electrophoretic and the chromatographic preconcentracion techniques, is that allow to determine these drugs at ng·L-1 levels. These results have been obtained by using the technique off-line SPE to preconcentrate the analytes and to clean-up the sample matrix before the application of the preconcentration technique. <br/><br/>Other strategy used to determine NSAIDs in the aquatic environment at low levels has been the use of MS as the detection system. This coupling allows confirming and identifying the presence of the analytes in the sample. So, it has been possible the determination of the studied drugs in surface waters and their identification in the STPs. In this study, the technique off-line SPE and the combination of liquid-liquid extraction (LLE) and off-line SPE off-line, respectively, have been used as the sample pretreatment technique.
Repositori URV