Doctor of Philosophy (PhD)
The goal of the research reported in this dissertation is to develop packed and open-tubular capillary electrochromatographic methods for improved achiral and chiral separations of various classes of analytes. The first part of this research involves the separation of seven benzodiazepines by the use of the packed mode of capillary electrochromatography (CEC) and a 40 cm packed bed of Reliasil 3 μm C18 stationary phase. Optimal conditions were established by varying the mobile phase, the amount of organic modifier, the buffer concentration, the applied voltage, and the column temperature. The second part of this research focuses on the open-tubular mode of CEC and the polyelectrolyte multilayer (PEM) coating approach. In the first study of this part, poly (diallyldimethylammonium chloride), PDADMAC, was used as the cationic polymer and poly (sodium N-undecanoyl-L-glycinate), poly (L-SUG), was used as the anionic polymer for the construction of the PEM coating. The performance of the modified capillaries as a separation medium was evaluated by use of seven benzodiazepines as analytes. In the second study, the anionic polymeric surfactant poly (sodium N-undecanoyl-L-leucylvalinate), poly (L-SULV), was used as the chiral discriminator for the separations of several drug analytes. Reproducibility of the PEM coating was evaluated by computing the relative standard deviation (RSD) values of the electroosmotic flow (EOF). The PEM-coated capillaries were remarkably robust with excellent reproducibilities and high stabilities against extreme pH values. The stability of the capillary surface was further investigated after exposure to NaOH solutions. The structural changes of these coatings were monitored using laser scanning confocal microscopy (LSCM). These changes were discussed in terms of separations using open-tubular CEC (OT-CEC). In addition, the electropherograms obtained from the chiral separation of 1,1’-binaphthyl-2,2’-dihydrogenphosphate (BNP) in OT-CEC allowed the measurements of both selectivity and electroosmotic mobility changes after long exposure to NaOH.
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Kapnissi, Constantina P., "Analytical separations using packed and open-tubular capillary electrochromatography" (2004). LSU Doctoral Dissertations. 595.