Determination of the zeta potential

The maximum is an activation barrier that prevents or reduces agglomeration. For a stable dispersion the particles must have a large charge and a high activation barrier. An experimental parameter proportional to this charge is the zeta potential. Therefore, the determination of the zeta potential is an important experimental procedure in characterizing the particles for co-deposition. 

For small spherical particles and dilute electrolytes the zeta potential is larger by the factor 1.5 

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The determination of the zeta potential of particles in a disperse system provides useful information concerning the sign and magnitude of the charge and its effect on the stability of the system (see Sec. II.B) [56, 206 208], It can be of value in the development of pharmaceutical suspensions, particularly if the... 

In order to utilize equation (17) for the determination of the zeta-potential, it may be written in the form... 

The original Acoustosizer used a single frequency whereas a later development has a range of 13 frequencies between 0.3 and 13 MHz. This allows the measurement of the dynamic mobility spectrum and the determination of the zeta potential and particle size. In order to invert the mobility spectrum into a size distribution a log-normal distribution of particle size is assumed. A comparison with photon correlation spectroscopy for determining particle size and laser Doppler anemometry for particle charge eonfirmed the results using ACS [266]. These and additional sedimentation measurements confirmed that changes in particle size and zeta potential due to dilution effects are likely to occur in aqueous and non-stabilized systems. 

This is why the determination of the zeta potential by different processes and a comparison of the values received may pose great problems. 

Capillary electrophoresis is the most used method for determination of the zeta potential of unmodified and polymer-modified diluted kaolin dispersions. 

Electro-osmosis is a kinetic process that is used for the determination of the zeta-potential of a surface/electrolyte solution interphase. It is also a process found in the sweat pores of... 

This effect has been the subject of considerable controversy. Subsequent studies using various methods were not conclusive as to the reality of the effect. Langmuir has proposed [46] that the anomalous results were due to a ehange in the effective diameter of the silica capillary owing to a layer of electrolyte immediately adjacent to the capillary wall, related to the zeta potential. Onsager [47] made an extended theoretical investigation of this effect and developed a quantitative theory of the influence of the zeta-potential on the capillary rise. His theory accounted for most of the Jones and Ray results and led to an accurate determination of the zeta-potential of quartz. An attempt to interpret the results as a pure surface tension effect has also been made [48]. Besides, it has been suggested recently [9] that an initial decrease in the surface tension could be attributed to a nonzero solubility of the salt in the vapor. 

Weber, K. Stahl, W. (2003) Determination of the zeta potential of a filter cake by means of permeation experiments. Chemical Engineering Technology, 26 (5), 549-553. 

Doren, A., Lemaitre, J., and Rouxhet, P. G. (1989) Determination of the zeta potential of macroscopic specimens using microelectrophoresis J. Colloid Interface Sci., 130, 146-156. 

The zeta potential of the formulations was determined by Doppler velocimetry and PCS on a Zetasizer 4 (Malvern Instruments, U.K.), without further dilution. The zeta potential of LC-AmB under these conditions was —44 mV, slightly lower than that measured for the same lipid composition without AmB, —55 mV, but remaining consistent with colloidal stability. This reduction in the absolute value of the zeta potential could be due to the presence of AmB at the surface, because free AmB dispersed in water under the same conditions had a less negative zeta potential about —27 mV. 

The Helmholtz-von Smoluchowski equation indicates that under constant composition of the electrolyte solution, the EOF depends on the magnitude of the zeta potential, which is determined by various factors inhuencing the formation of the electric double layer, discussed above. Each of these factors depends on several variables, such as pH, specihc adsorption of ionic species in the compact region of the double layer, ionic strength, and temperature. 

Quantitatively, the pH determines on the solid side the value of the zeta potential related to the concentration of charged surface sites (Fig. 3). On the liquid side, it allows selection of the most abundant metal... 

If the solid material is a substance capable of ionization, then the sign and magnitude of the zeta-potential may be determined by such ionization. 

FIG. 2 pH dependence of the zeta potential of a commercial kaolin dispersion determined by means of capillary electrophoresis ( ) and acoustophoresis (o). 

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