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

A procedure to reduce electroosmotic flow (EOF) in 25-μm inside diameter (i.d.) fused silica capillaries has been developed for use in capillary sample introduction to narrow channels. The surface of 25-μm i.d. fused silica capillaries has been modified with an acrylamide polymer developed since commercially coated 25-μm i.d. fused silica capillaries are not available. These coated capillaries enable DNA to migrate through the capillary, against electroosmotic flow, and continuously separate in ultrathin channels. Initial experiments have focused on measuring the rate of EOF in the sampling capillary using capillary electrophoresis (CE). Later experiments have combined CE with channel electrophoresis and laser induced fluorescence detection for the detection of size-based fragments of Hae III-digested double stranded DNA (dsDNA). This technique combines the parallel processing capabilities of channel electrophoresis with the advantages of sample introduction using a single capillary. Ultrathin channels, 25-μm thick, allow for the efficient dissipation of Joule heat, increased separation potentials, and decreased separation time. This research demonstrates that coated 25-μm i.d. capillaries can be used as transfer devices to smaller ultrathin channels for the detection of DNA fragments.