Zeta potential and size measurement of nanoparticles by laser scattering video microscopy:
– Ionic end groups at the interfaces of molecules or particles prevent Van der Waals attraction:
+ A short-range force causing a coating of surfaces, coagulation, aggregation, flocculation, and coalescence of colloids and dispersions.
+ The higher the electrostatic repulsion between particles, the lower is the probability for collisions of Van der Waals type.
+ A great amount of formulation work is directed to the optimization of particle interfaces for dispersion stability and good dispersibility.
+ One part of it is the control of the electrokinetic behavior of the dispersions and macromolecular solutions.
– The presented ZetaView® revives the direct measurement offered by a micro – electrophoresis set-up to a new attraction.
– Laser illumination, auto-alignment, direct visualization, and tracking of the moving particles by video analysis are the tools to achieve this.
– Nearly any surface carries an ionic charge.
– If it is sufficiently high, particles repel each other keeping a dispersion stable.
– Immersed in water, the charge is immediately compensated by surrounding ions, forming an electrostatic double layer.
– Although it is neutral from the outside, the double layer can be peeled off quite easily by physical arrangements such as electrophoresis, ultrasonic vibration, mechanical shearing, and others.
– By applying these techniques, the ionic charge of the interface is measurable as a particle interface potential PIP, indicating dispersion stability or instability.
– In this contribution, the “streaming potential” sense is presented as an effective tool to map the electrostatic behavior of polyelectrolytes and particles.
– A signal measurement and mixing of titrant solution to the sample is achieved within 5 seconds, one complete titration can be performed within 5 minutes.
– The method can be applied to polyelectrolyte solutions (size > 0.5 nm) and to dispersions up to 300 µm particle size.
– To be correct, when going from small to big particles the method changes gradually from streaming to an “inertia potential” sensing.
– 0.1 g is needed as a minimum sample quantity. Concentrations up to 40% are possible, bearing in mind that high viscosity is a limitation.
– The result correlates to zeta potential in many cases, yet has to be proven for a given sample class.
– Stabino® II: Zeta potential and charge titration for rapid assessment of stability and formulation of colloids
– NANO-flex® II: Nanoparticle Measurement Device for Particle Size Distribution with 180° DLS Dynamic Light Scattering
– StabiSizer®: Size distribution, zeta potential, and charge titration for rapid assessment of stability and formulation of colloids
– ZETA-check: Zeta Streaming Potential