화학공학소재연구정보센터
Langmuir, Vol.17, No.17, 5314-5318, 2001
Measurement of wall zeta potentials and their time-dependent changes due to adsorption processes: Liposome adsorption on glass
A novel method of measuring the zeta potential associated with the planar glass surface of an electrophoresis cell by laser Doppler velocimetry has been developed. The method exploits the observation that the terminal velocity of particles subjected to an electric field is reached at least an order of magnitude more quickly than the establishment of electroosomotic flow at the planar glass surface of the cell. By using a fast field reversal technique so that the particle velocity is unaffected by electroosomic flow in conjunction with a mixed mode measurement, it is possible to obtain the electrophoretic mobility of a particle without the need to make measurements at the stationary layer. In addition, the methods give data for the zeta potential at the cell wall. The cell wall zeta potential is sensitive to adsorption of solutes from solution and may be used to follow both the kinetics of adsorption and to construct an adsorption isotherm. The method has been applied to the study of the adsorption of cationic and anionic phospholipid liposomes. The wall zeta potentials reflect the adsorption process in that the cationic liposomes cause a reversal of the wall zeta potentials from the negative value of the clean glass surface to positive values after 1-3 h. In contrast, the anionic liposomes increase the negative wall zeta potentials. At equilibrium, limiting potentials may be fitted to a Langmuir isotherm. The results from the fitting are compared with the adsorption of liposomes to silica particles in suspension.