A fast growing field of application for microstructures is analytical chemistry. The goals are to enhance and improve existing methods and techniques by implementing them on microchips, and to develop new concepts to keep up with the pace of current technologies in synthetic and pharmaceutical chemistry, where combinatorial libraries produce enormous amounts of reaction products, which need to be checked and investigated. Similar tasks are encountered in biochemistry and biomedicine, where a high through-put of sample is necessary, with, at the same time, only tiniest amounts available. Manipulations of liquids in a micromachined channel manifold can be performed in a precise and efficient way using the phenomenon of the electroosmotic flow. By applying computer-controlled voltages at the terminals of the channels, it is possible to perform such basic operations as injecting and mixing of liquids. In appropriately designed microchips various liquid handling protocols can be implemented for sample pre-treatment procedures as well as elaborate separation techniques. Amongst the most promising techniques are solid-phase extraction for sample concentration and clean-up, and a suite of electrophoretic and chromatographic methods for the separation of complex sample mixtures. We are developing several modules, which will help to arrive at fully integrated miniaturized chemical analysis systems. The focus is on the introduction of novel chromatographic phase materials to the microchips, the application of sophisticated liquid handling protocols, the combination of several aspects of the analytical process on a single device, and the realization of two-dimensional separation techniques.
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