Determination of Stability and Particle Size of Colloids in Lab or Online - poster
André Giese, Kai Gossmann, Philipp Schreier, Margret Böck, Hanno Wachernig
Colloid Metrix GmbH, Meerbusch, Germany
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In addition to the final product properties, the main objective in the formulation of colloidal dispersions is the particle size and the stability against agglomeration.
The particle size is of great importance, but also their chemical environment.
For this purpose, the zeta potential, which is generally regarded as a measure of the mutual repulsion of the particles by electrostatic interactions, is a key parameter. The zeta potential and thus the stability of dispersions is influenced by the suspension properties. By autotitration, the formulator can investigate the influence of pH, salt concentration and additives on stability, and optimize the required quantities accordingly.
The determination of the particle surface charge is often also of great interest. It allows an estimation of free binding sites or adsorption capacity that can be used for the functionalization of the particles, be it for further stabilization against aging processes or for changing the final product properties.
This kind of characterization can be optimally performed with the streaming potential / streaming current method in combination with an autotitration, even at high particle concentrations. At such concentrations, the 180° heterodyne dynamic light scattering method is suitable for determining particle size, as it is less susceptible to multiple scattering effects.
On an industrial scale, inline particle size measurement can be interesting. The DLS method mentioned above can be extended to monitor top-down or bottom-up processes in real-time.