Characterization of electrophoretic sample injection and separation in a gel-filled cyclic planar microstructure

The data presented in this paper demonstrate that it is possible to fill a cyclic micrometer-dimensional channel system formed in untreated glass with an acrylamide solution, to produce a gel matrix consisting of linear, noncrosslinked polyacrylamide (LPA) and to perform highly reproducible capillary gel electrophoretic separations with submicrometer plate heights within a few seconds. In such a system, no fluid flows are present and mass transport is based upon electrophoresis and diffusion only. Using a video system, an 8% LPA matrix and fluorescein isothiocyanate labelled amino acids as test compounds, sample introduction and separation could be visualized and volume-defined, unbiased electroinjection from a 12 pL intersection of two channels via application of counter voltages could be optimized. Using laser-induced fluorescence solute detection, the cyclic gel-filled microstructure is shown to permit stable cyclic operation, an effective approach which simulates longer capillaries with improved separations at relatively low voltages. Furthermore, employing fluorescent phosphorothioate anti-sense oligonucleotides, a 10% LPA matrix is demonstrated to be able to sieve and thereby separate oligonucleotides comprising more than five bases.