See Membrane Characterisation Equipment

Particle Size Measurements <100nm

Particle Size measurements <100nm, Zeta Potential, and molecular wieght measurements

Particle size analysis or particle sizing is the procedure which determines the size range, and/or the average, or mean size of the particles in a powder or liquid sample. This is suitable for characterisation of nanoparticles, colloidal dispersions, polymer and protein solutions.

Dynamic Light Scattering (DLS) is used to measure particle 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. Non-Invasive Back Scatter technology (NIBS) is incorporated to give the highest sensitivity simultaneously with the highest size and concentration range.

The technique is ideal for the measurement of the size of colloids, nanoparticles and molecules, without requiring agitation to make the sample suitable for analysis.

From the size, an estimate of the molecular weight can be made, which has the benefit of being faster to confirm oligomeric state than size exclusion chromatography (SEC).

Zeta potential

The Zetasizer also incorporates a zeta potential analyzer that uses electrophoretic light scattering for particles, molecules and surfaces, and a molecular weight analyzer using static light scattering.

Laser Doppler Micro-electrophoresis is used to measure zeta potential. An electric field is applied to a solution of molecules or a dispersion of particles, which 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 and zeta potential distribution.

A surface zeta potential accessory uses tracer particles to measure electro-osmosis close to a sample surface to calculate the zeta potential of the surface.

Molecular weight

The Zetasizer Nano series enables you to measure the molecular weight of macromolecules in solution using Static Light Scattering (SLS). The SLS technique requires the system to be sensitive and exceptionally stable, so the Zetasizer has been designed to meet these criteria. The Zetasizer measures the average molecular weight of the sample. In comparison, size exclusion chromatography separates the components of a sample before the calculation of an accurate molecular weight distribution.


In house: Zetasizer Nano-ZS Malvern Instruments