Advanced systems

Abstract

The benefits of miniaturization have been realized in the field of electrophoresis by using capillaries instead of cylindrical hollow tubing or slab gels. An additional miniaturization has been demonstrated by the use of photolithographically fabricated microstructure by Ciba Geigy [1, 2]. Photolithographic patterning on the silicon wafer has become a well-known technique in microelectronics and has been applied to gas and liquid chromatography. The process generally consists of the exposure of silicon wafer coated with photoresist to light through a metal mask followed by etching the exposed glass with a HF-based solution. Capillaries can be formed by covering the fabricated glass with other glass plate [1]. Capillary electrophoresis on a planar chip with a highly flexibile design is feasible by the fabrication of complicated microstructures. Manz and co-workers reported preliminary micro-CE on a 15cm × 4cm chip, which provides separation on a minute scale [1, 3, 4]. When the scale was decreased to 2cm × 1cm fluorescent labeled amino acids could be separated with up to 75000 theoretical plates in 15s [2] and with up to 6800 theoretical plates in 4s [5]. Fast and efficient separation of fluorescent labeled amino acids was presented by changing the separation length of the capillary to between 5 to 50mm and the applied potential with an integrated sample injection of 100 pl, which resulted in an analysis from a few seconds to a few tens of seconds with theoretical plate numbers of 5800 to 16000, respectively [6–8].