IMAGE-ANALYSIS DETERMINATION OF PARTICLE-SIZE DISTRIBUTION

Three different methods for the determination of particle sizes by means of light microscopy combined with image analysis have been evaluated for dispersions of spherical starch particles. (i) Individual particles. This method was used to separate particles that formed clusters into individual particles. The size of the particles was determined by the diameters of the circles which could be inscribed in the cluster. (ii) Clusters. This method was used to measure all the connecting particles as one object, regardless of whether they were separated or in clusters. The area of the clusters was measured and the diameter of an equivalent circle was calculated. (iii) Strings of beads. This is a special case of clusters where particles were associated in one direction and formed strings. The diameter was the maximum distance between two parallel lines touching the object. Statistical evaluation of the results showed that there was very little variance between slides, frames and samples from the same batch. Thus repeated measurements with the image analysis system appear to be accurate. For the three image analysis methods the mean values of the particle size were between one micron to three microns.