*MT 187 - Particle size analysis by laser diffraction


Content Handbook K


Outline of method

A representative sample, dispersed at an adequate concentration in a suitable liquid or gas, is passed through the beam of a monochromatic light source, usually a laser. The light scattered by the particles at various angles is measured by a multi-element detector and numerical values relating to the scattering pattern are then recorded for subsequent analysis. These numerical scattering values are then transformed, using an appropriate optical model and mathematical procedure, to yield the proportion of total volume to a discrete number of size classes forming a volumetric particle size distribution.




This method provides guidance on the measurement of particle size distributions of crop protection formulations, for example granules, powders, suspensions and emulsions, through analysis of their angular light scattering patterns. Detailed descriptions for the use of laser diffraction methods are given in ISO 13320-1.