The zeta potential is an important parameter for assessing the stability of a liquid suspension or emulsion, among other things. In principle, it indicates the electrical potential of a particle in dispersion at the shear plane to the dispersing medium—usually water or an organic solvent. A high zeta potential means a strong repulsive force between two particles that are approaching each other in dispersion. This prevents agglomeration or coagulation, and the system is stable. If, on the other hand, the zeta potential is close to zero (isoelectric point, IEP), the dispersion is unstable and flocculates. There are basically two methods for measuring the zeta potential: electrophoretic light scattering (ELS) and electroacoustics. The selection of the appropriate method depends primarily on the application.
Electrophoretic light scattering (ELS) is ideal for measuring the zeta potential of dispersions used in biochemistry, biotechnology, pharmacy, and food technology. In this method, as implemented in the BeNano series devices, the zeta potential is measured by measuring the mobility of the particles in an electrophoresis cell using a laser via the laser Doppler effect. The special PALS technique (phase analysis light scattering technology) also allows measurements to be carried out in non-polar or highly conductive systems.
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| BeNano series Zeta potential measurement – ELS (ISO 13099-2) |
The electroacoustic method is designed for highly concentrated, even sedimenting dispersions, especially in the hard material sector (cements, battery slurries, ceramic suspensions). In this method—implemented in the DT-300/310/330 series devices—the zeta potential is determined by measuring the microcurrent of the dispersion, which is generated by coupling an ultrasonic wave of a specific frequency (CVI method). The sample can be in flow (stirring, pumping) or at rest.
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| DT-300/310/330 series Zeta potentia measurement – electroacoustics (ISO 13099-3) |
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