Isopycnic focusing study of the transient and equilibrium states in the settling of colloidal particles generated by coupled electric and gravitational fields

Abstract

The combination of the electric field to form a density gradient in a suspension of the charged colloidal particles with the gravitational field forces to focus the large-size uncharged particles into isopycnic layers was used to study the kinetics of the formation of the density gradient. Isopycnic focusing of coloured density marker beads was used to visualize the evolution and the final quasi-equilibrium shape of the density gradient formed in a suspension of the silica particles. The influence of the electric field intensity, of the average concentration of the colloidal silica particles, and of the electrolytes combined with two different electrode systems was investigated under conditions of static thin layer focusing. The experimental results obtained under model static conditions should allow the understanding of the processes governing the isopycnic or more general isoperichoric focusing in thin layers under dynamic flow conditions.

References

1. A. Kolin, in Electrofocusing and Isotachophoresis, ed. B. J. Radola and D. Graesslin, de Gruyter, Berlin, 1977.
2. J. Janča, Makromol. Chem., Rapid Commun., 1982, 3, 887.
3. J. Janča, Mikrochim. Acta, 1994, 112, 197.
4. J. Janča and R. Audebert, Int. Symp. Polym. Anal. Charact., Inuyama, Japan, 1992; J. Appl. Polym. Sci., Appl. Polym. Symp., 1993, 52, 63.
5. J. Janča and M. Špírková, J. Colloid Interface Sci., 1996, 184, 181.
6. R. J. Hunter, Zeta Potential in Colloid Science, Principles and Applications, Academic Press, London, 1981.
7. J. Janča and R. Audebert, Mikrochim. Acta, 1994, 113, 299.
8. J. Janča, J. Colloid Interface Sci., 1997, 189, 51.
9. M. Mason and W. Weaver, Phys. Rev., 1924, 23, 412.
10. W. Weaver, Phys. Rev., 1926, 27, 499.
11. G. M. Nazarian, J. Phys. Chem., 1958, 62, 1607.
12. J. Janča and R. Audebert, Mikrochim. Acta, 1993, 111, 163.
13. G. K. Batchelor, J. Fluid Mech., 1972, 52, 245.
14. H. J. H. Clercx and P. P. J. M. Schram, J. Chem. Phys., 1992, 96, 3137.
15. K. D. Caldwell, L. F. Kesner, M. N. Myers and J. C. Giddings, Science, 1972, 176, 296.
16. K. D. CaldwelLand and Y. S. Gao, Anal. Chem., 1993, 65, 1764.
17. Capillary Electrophoresis: Theory and Practice, ed. P. D. Grossman and J. C. Colburn, Academic Press, New York, 1992.
18. P. Delahay, Double Layer and Electrode Kinetics, Wiley, New York, 1965.
19. J. Koryta and J. Dvořák, Principles of Electrochemistry, Wiley, New York, 1993.
20. C. G. Konif, E. M. F. Van Iersel, A. Vrij and W. B. Russel, J. Chem. Phys., 1985, 83, 4717.
21. J. Janča and M. Špírková, Collect. Czech. Chem. Commun., 1996, 61, 819.