Improving product stability
The stability of particle dispersion will depend upon the balance of the repulsive and attractive forces that exist between particles as they approach one another. If all the particles have a mutual repulsion then the dispersion will remain stable. However, if the particles have little or no repulsive force then some instability mechanism will eventually take place e.g. flocculation, aggregation etc.
The zeta potential of a particle is the overall charge that the particle acquires in a particular medium and can be measured on a Zetasizer instrument. The magnitude of the measured zeta potential is an indication of the repulsive force that is present and can be used to predict the long-term stability of the product. If all the particles in suspension have a large negative or positive zeta potential then they will tend to repel each other and there is no tendency for the particles to come together. However, if the particles have low zeta potential values then there is no force to prevent the particles coming together and flocculating. The effect of the pH, concentration of an additive or the ionic strength of the medium on the zeta potential can give information in formulating the product to maximise stability.
In addition, the particle size of the suspension can also be measured in a Zetasizer instrument. This provides information on the state of the dispersion and can be used in association with the zeta potential measurements to formulate the product to prevent flocculation and improve long term stability.
Presentations:
On demand presentation on "Predicting Formulation Stability with the Zetasizer Nano System ". For industries involved in the production of colloidal dispersions, the long-term dispersion stability is an important characteristic of the final product. The stability of a particle dispersion will depend upon the balance of the repulsive and attractive forces that exist between particles as they approach one another. The magnitude of the electrostatic interactions between particles can be determined by measuring the zeta potential of the particle dispersion and hence zeta potential measurements can be used to predict dispersion stability. This presentation describes the application of zeta potential measurements in predicting dispersion stability.
On demand presentation on "Why measure Zeta Potential?" This presentation provides an overview of what zeta potential is, what affects it and how it is measured. The use of zeta potential in predicting dispersion stability is also discussed and illustrated with application examples.
On demand presentation on:"What Affects Dispersion Stability and How Can We Predict It?". The stability of a particle dispersion is determined by the balance between repulsive and attractive forces which the particles experience as they approach one another. This presentation discusses how dispersion stability can be achieved, what factors influence it and how an understanding of these factors can be used to predict the shelf life of a product.
Application notes:
Photon Correlation Spectroscopy and Microemulsions. Microemulsions are colloidal dispersions that can be used for the solubilisation of drugs. In order to ensure safe and efficient dosage, predictable shelf life and batch to batch consistency, particle size must be closely controlled. One technique that can be used for size determination of microemulsions is that of photon correlation spectroscopy (PCS).
Characterization of Protein Polyelectrolyte Complexes. This application note highlights the use of the Malvern Zetasizer Nano system for characterization of proteinpolyelectrolyte complexes (PPCs).
Emulsions: Predicting the Stability of Emulsions. Measurements of zeta potential, along with particle size, can be used to predict the stability of fat emulsions.
