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Stabino® -Efficient Stability Analysis System for Colloids and Dispersions

Stabino® -Efficient Stability Analysis System for Colloids and Dispersions

Stabino® Particle Charge Titration via Streaming potential for Determination of Dispersion Stability

Rapid charge titrations for stability analysis of colloids and dispersions enhance the efficiency of formulation and particle interface analysis. The Particle Interface Potential of particles is measured as streaming / zeta potential and represents the degree of electrostatic repulsion between particles. It reacts to pH, conductivity and polyelectrolyte surrounding, respectively. A charge titration with the Stabino® specifies which parameters require special attention. The isoelectric point can be titrated within short time, gathering information on charge density and stable zones, whilst pH, conductivity and temperature are monitored simultaneously.

Method

The “heart” of the Stabino® is a cylindrical PTFE chamber with an oscillating piston, both carrying only very little anionic charge at the surface (Figure 1). The cylinder contains the 10 mL sample. The addition of titrands is controlled via two incorporated precision titration pumps delivering titrand solution from one or the other reservoir.

Stabino principle
Figure 1:
Sample cell with oscillating piston and oscillating streaming potential SP

A fraction of the particles in the cell is immobilised at the surface of the wall. Therefore, with the piston movement Δv, the mobile cloud of the double layer of the immobilised particles is pushed up and down. That oscillating ion cloud produces an alternating voltage SP = streaming potential at the two electrodes. It is proportional to the zeta potential of the particles.

The Particle Interface Potential, like the streaming potential measured in Stabino®, represents the degree of electrostatic repulsion between particles and reacts to pH, conductivity and the polyelectrolyte surrounding, respectively. Any or all of these parameters can cause a material system to shift. The titration result is characteristic for the sample in a certain chemical environment. A charge titration with the Stabino specifies which parameters require special attention.

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