Micro-structured analytical instrumentation for the analysis of liquids

Micro-structured analytical instruments are designed for manipulating and transporting fluids and biological entities. In the near future they will form the key element for so-called micro Total Analysis Systems. Conventionally, these elements are made from glass or silicon by wet-etching. In comparison to these materials, a much wider range of micro-structuring technologies is available for plastic materials. Polymers have the additional advantage of being readily replicable with low-cost methods such as injection molding or hot embossing. Functioning microchips for different purposes were produced this way. An advantage of micro-structured analytical instruments is the handling of ultra-small volumes. In some cases this can result in inappropriate detection limits. Two concepts to overcome this problem are demonstrated: an on-column conductivity detector and the coupling of microchips with mass spectrometry. To achieve a higher sample load capacity compared to miniaturized separation devices for capillary electrophoresis, isotachophoresis is applied. Isotachophoresis is used as a separation technique in itself and as a sample preconcentration technique in combination with capillary electrophoresis. (C) 2002 Elsevier Science B.V. All rights reserved.