MEASUREMENTS ON THE DIFFUSION-COEFFICIENT OF COLLOIDAL PARTICLES BY TAYLOR-ARIS DISPERSION

Taylor-Aris dispersion in narrow-bore capillaries is used to measure t he diffusion coefficient of colloidal particles in aqueous suspension. The method is shown to yield accurate results for particles up to abo ut 0.3 mu m in diameter; the measurement time for larger particles is prohibitively long and impractical. For hydrophobic particles, interac tions with the capillary walls can introduce error into the interpreta tion of the data. The measurements also suggest that buoyancy-driven p article motion can introduce error. Consequently, a method similar to capillary hydrodynamic fractionation was developed to establish when t hese factors were of negligible effect. The results constitute an orde r-and-a-half improvement in the sensitivity of the technique, which ha s been recently shown to work for nanometer-sized proteins. The data s uggest that, when matched with the appropriate theory, dispersion in c apillaries may be a useful probe of colloidal and gravitational intera ction potentials. (C) 1997 Academic Press.