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Cations in the diffuse layer are also attracted by the negatively charged particle but to a lesser extent, since the interactive force between two charged particles is proportional their charge magnitudes, and inversely proportional to the distance that separates them. A tight layer of counter ions (in this case cations) called the stern layer, forms around the surface of the particle, where its attractive forces are strongest. To take a closer look, the graphic to the left depicts a negatively charged particle dispersed in water. Low inter-particle repulsion will enhance flocculation and aid in proper filtration. On the other hand, low zeta potential is sometimes desired, e.g. If the suspended particles have a large magnitude of charge, they will likely repel one another and have lower tendencies to flocculate, indicating stability and long term shelf life. Zeta potential is often helpful in terms of ruling out candidate product batches during stability testing thereby saving time and money.

3 It is then used to calculate the zeta potential by applying the Henry equation: Their velocity, or electrophoretic mobility, under the influence of an electric field, is measured using LASER Doppler velocimetry. During a zeta potential analysis, charged colloidal dispersions are placed into a zeta cell (Figure 1) and upon application of an external electric field, the particles travel toward the electrode that has a charge opposite to that of the particle. 2 At PTL, zeta potential is measured using the Zetasizer Nano ZS (Malvern Panalytical), which calculates zeta potential using the principle of electrophoresis. Under the influence of an electric field, charged particles will exhibit certain electrokinetic effects including electrophoresis, electroosmosis, streaming potential, or sedimentation potential. Zeta Potential is the characterization of the electrokinetic potential of liquid-liquid or solid-liquid colloidal dispersions.

Full descriptions on usag e and application are contained in the sub. The accessories available for use with the Zetasizer Nano are indicted in the fol- lowing section. This manual focuses on specific issues of the Zetasizer Nano accessories that are not covered by the above manuals.