Anton Paar has published an application note on the use of its Litesizer 500 particle analyser in determining three particle sizes using Dynamic Light Scattering (DLS).
Particles in a liquid suspension undergo random or Brownian motion, the speed of which is directly related to the size of the particles; the smaller the particles, the faster they move. When light passes through a particle suspension, the movement of the particles produces fluctuations in the intensity of scattered light. Detection and analysis of the light-scattering fluctuations allows us to calculate the particles'
radius.
Polymer latex spheres can be used to verify DLS performance because they are available as well-characterised dispersions of near-perfect spheres.
While DLS is a well-established technique for determining the average radius of a monodisperse sample, it is a significant challenge to distinguish particles with different sizes in a single suspension. The ability to resolve multiple particle sizes depends on several factors, including the sizes of the particles, their relative scattering intensities, the polydispersity of their size distributions, the quality of the sample preparation, and the quality of the data.
