Studies of electrophoretic separations of DNA restriction fragments by capillary electrophoresis in solutions of (hydroxyethyl) cellulose (HEC) were performed. Rheological studies were used to confirm that the entanglement threshold (phi*) for the HEC solutions used is approximately 0.004 g/mL, in good agreement with theoretical predictions. A mesh size an order of magnitude smaller than that found in agarose gels (on a per weight basis) was calculated using polymer-entanglement theory and was confirmed by electrophoretic measurements. Electrophoretic migration was shown to follow the Ogston regime under most conditions. An approach for obtaining smaller mesh sizes is presented.

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Capillary electrophoresis (CE) continues to grow rapidly as an analytical technique in a wide range of application areas (1-5). Typically, CE separations are performed in fusedsilica capillaries with internal diameters of 25-100 pm. High heat dissipation efficiencies in the narrow columns allow separations to be performed at high field strengths (200-500 V/cm), resulting in short analysis times and peak efficiencies of up to millions of theoretical plates.

The effect of molecular orientation on the electrophoretic mobility of rod-shaped polylons as measured by free solution capillary electrophoresis is studied by using the tobacco mosaic virus (TMV) as a model solute. This orientational dependence of molecular mobility is measured by observing the influence of electrical field strength (up to 400 V/cm) on the electrophoretic mobility of TMV. The electrophoretic mobility of TMV increases with increasing field strength. This increase can be quantitatively correlated with the decrease in the translational frictional coefficient (f) due to the increasing alignment of TMV with the electric field. A model is developed relating the decrease in f to the alignment of TMV with the electric field through its polarizability and aspect ratio. To confirm the observed orientational affects on mobility, control experiments were performed with 0.364 micron diameter Latex spheres. Due to their spherical symmetry, no orientational effects would be expected. Indeed, no increase in mobility was observed for these spherical particles. Calculations are presented to demonstrate that the increase in mobility is unlikely to be caused by either the Wien effect or any temperature variation resulting from Joule heating of the electrophoresis buffer.

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