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Malvern Zetasizer NanoZS zetameter / DLS

Technical specifications

Zetametry

The device uses light scattering to measure the electrophoretic mobility of particles subjected to the application of an electric field. Henry’s law can be used to determine the zeta potential of particles from their electrophoretic mobility, given the viscosity and dielectric constant of the dispersion medium.

Zeta potential is the electrostatic potential measured at the hydrodynamic diameter (or shear plane) of particles suspended in a liquid medium. It allows us to characterize the electric charge in the vicinity of the particle surface, depending on its environment.

Applications

Measurements of zeta potential as a function of various parameters (pH, ionic strength, etc.) provide information on particle interactions. In particular, these measurements can be used to predict the behavior of emulsions and colloidal dispersions (stability, flocculation, coalescence, etc.), and thus to solve certain formulation problems.

They are also extremely useful for determining the mode of interaction between suspended particles and charged species present in solution. This makes it possible to characterize the behavior of certain ions in contact with a charged surface: specific adsorption leading to the formation of surface complexes, or purely electrostatic interaction.

Technology: electrophoretic light scattering (ELS), determination of electrophoretic mobility by phase analysis and mixed-mode measurement (M3-PALS);
Laser: He-Ne (633 nm), detection at 13°;
Size range: diameter between 4 nm and 10 μm;
Temperature range: 10-90°C;
Plastic cuvette volume: approx. 1 mL;
Potential analyses in non-aqueous media with specific cell (dip-cell);
The device is coupled to an automatic titrator (MPT-3) fitted with a pH probe, enabling controlled quantities of electrolytes to be added to vary pH and/or ionic strength.

Dynamic Light Scattering (DLS)

Quasi-elastic light scattering granulometry measures the diameter of particles between 0.3 nm and a few µm, suspended in a liquid. This method is based on the determination, by light scattering, of the velocity of colloidal particles when subjected to Brownian motion. The device records fluctuations in light scattered by moving particles as a function of time. This signal is then mathematically processed to generate an auto-correlation function, which is used to determine the translational diffusion coefficient of the particles. This is directly related to their size by the Stokes-Einstein law. This technique gives access to the hydrodynamic diameter of the particles, which takes into account the solvation layer in the vicinity of the surface. Its size depends on various factors, in particular the ionic strength of the dispersion medium.

Dual-angle particle and molecule size analyzer (13° and 173°);
NIBS technology for improved aggregate detection and measurement of small or dilute samples, as well as samples with very high or very low concentrations;
Measurement range: 0.3 nm to 10 µm;
Incident wavelength: 633 nm (He-Ne laser);
Cell volume (polystyrene or quartz): 1 mL;
Temperature range: 10-90°C;
Autocorrelation function processing algorithms: Cumulants, Contin, NNLS;
Static light scattering analysis with Debye model (molecular weight determination).

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