Measurement of the Size Distribution of Multimodal Colloidal Systems by Laser Diffraction

Laser diffraction (LD) is a well-established tool for the measurement of particle size distribution. Recently, its demand and use for the measurement of complex biological systems have increased. Among the challenges that these types of samples present, there is the presence of multiple particle populations whose modal size may span across several orders of magnitude. In this study, we assessed the accuracy of LD for the measurement of the modal diameter of both single and mixed populations of polystyrene particles with diameters ranging from 60 nm to 40 μm. We discuss the application of different available algorithms to the analysis of the data and their impact on the measurement results. Independent methods were applied to guide the selection of the algorithms and validate the measured size distributions. We found that the modal diameters of the particle size distribution measured by LD for the mixed suspension was accurate within 2 % for particles larger than 1 μm and generally within 25 % for the particles tested. Method repeatability was found to be robust, with deviations below 1%. The method was also found to be useful for estimating the relative concentration of the particle populations in the mixed samples. This study provides confidence in the use of LD for the measurement of complex multimodal colloidal samples.