| Sensitive, selective, and cost-effective analysis of biomolecules (phenols, amino acids, etc.) is important in clinical, environmental, and industrial fields. Capillary electrophoresis (CE) is one of the most used analytical techniques offering high performance, reagent economy, speed, automation capabilities, and miniaturization. At the microchip scale, CE also provides custom design, reduced consumption of reagents and sample, low waste generation, increased analysis speed, and portability. In this proposal the analysis by microchip-CE was divided in two main steps: the separation step and the detection step. The main goal of this dissertation was to investigate different strategies to improve the analytical performance of both of these steps. Based in the stated goal, the specific aims of the current dissertation were to investigate: (1) the electrophoretic/electrochemical effects of different surface coatings. (2) the interaction of selected enzymes with nanomaterials. Regarding the dynamic modification of the capillary surface, a very simple method for the coating of fused silica capillaries with a natural clay was developed. Some remarkable advantages of this coating procedure include stability, constant mu EOF at alkaline pH values, low cost of the reagents employed, and the possibility of using it in microchip devices. On the other side, the electrophoretic effects of surfactants with different chain lengths were also studied as a dynamic modification for the separation of six phenolic compounds. As a result of the adsorption of surfactants to the PDMS surface, reductions in the migration times and improvements in peak skew (S) were observed for all the surfactants when compared to bare PDMS. Surfactants offer a convenient and versatile approach to decrease analyte-wall interactions, improve peak shape, and decrease analysis time. Regarding the electrochemical detection, the addition of anionic surfactants can also produce improvements in the electrochemical detection of some phenolic compounds by enhancing interactions between the analyte and the electrode surface. |
