The Zetasizer Nano ZS90 incorporates three techniques in a single compact unit, and has a range of options and accessories to optimize and simplify the measurement of different sample types.
Dynamic Light Scattering at a scattering angle of 90 degrees is used to measure particle size and molecule size. This technique measures the diffusion of particles moving under Brownian motion, and converts this to size and a size distribution using the Stokes-Einstein relationship.
Laser Doppler Micro-electrophoresis is the technique used to measure zeta potential. An electric field is applied to a solution of molecules or a dispersion of particles, which will then move with a velocity related to their zeta potential. This velocity is measured using a patented laser interferometric technique called M3-PALS (Phase analysis Light Scattering). This enables the calculation of electrophoretic mobility, and from this, the zeta potential for the accurate measurement of a wide range of sample types and dispersion media including high salt concentrations and non-aqueous dispersants.