This proposal aims at the development of hydrophilic, hydrolytically stable wall coatings for plastic microchips made from poly (methyl methacrylate) (PMMA) and/or polycarbonate (PC). In analytical chemistry of the last decade, miniaturization of analytical operations and their integration on a microchip has become a hot topic. Capillary electrophoresis (CE) has been involved at the forefront of these efforts frequently. However, the miniaturization of the channel size emphasizes the influence of chemical properties of the channel surface. Therefore a negative charge that is inherently present at the surface results in adsorption of analytes on the channel wall and also in electroosmotic flow that is driven by these functionalities and compromises high-resolution CE separations. So far only a few coatings have been applied to glass and plastic microchips. This project will develop a hydrolytically stable, hydrophilic wall coating for plastic microchips made from PMMA and/or PC. The proposed coating will not carry any charge and will thus eliminate electroosmotic flow and minimize adsorption of analytes on the channel wall. As the top layer it will contain either natural polysaccharides locust bean gum or guaran, or a synthetic polymer poly (acryloyl diethanolamine) attached by thermal immobilization. We will characterize this coating by measuring its electroosmotic mobility JIEEO (< 0.5 * 10-9 m2V-1s-1) and stability after a treatment with NaOH solutions. We will demonstrate the utility of this coating by isoelectric focusing of model proteins and by CE of M13mp18 DMA sequencing fragments.
