Separations of DNA fragments with a coated 25-mu m capillary coupled to a 25-mu m high open channel

A procedure to reduce electroosmotic flow (EOF) in 25-mu m inside diameter (i.d.) fused silica capillaries has been developed for use in capillary sam ple introduction to narrow channels. The surface of 25-mu m i.d. fused sili ca capillaries has been modified with an acrylamide polymer developed since commercially coated 25-mu m i.d, fused silica capillaries are not availabl e. These coated capillaries enable DNA to migrate through the capillary, ag ainst electroosmotic flow, and continuously separate in ultrathin channels. Initial experiments have focused on measuring the rate of EOF in the sampl ing capillary using capillary electrophoresis (CE). Later experiments have combined CE with channel electrophoresis and laser induced fluorescence det ection for the detection of size-based fragments of HaeIII-digested double stranded DNA (dsDNA). This technique combines the parallel processing capab ilities of channel electrophoresis with the advantages of sample introducti on using a single capillary. Ultrathin channels, 25-mu m thick, allow for t he efficient dissipation of Joule heat, increased separation potentials, an d decreased separation time. This research demonstrates that coated 25-mu m i.d. capillaries can be used as transfer devices to smaller ultrathin chan nels for the detection of DNA fragments. (C) 1999 John Wiley & Sons, Inc.