Determining Particle Size Distribution of Polystyrene Latex (PSL) in Aqueous Salt Solutions

The DelsaNano​ series is a new generation of instruments that use photon correlation spectroscopy (PCS), which determines particle size by measuring the rate of fluctuations in laser light intensity scattered by particles as they diffuse through a fluid, for size analysis measurements and/or electrophoretic light scattering (ELS), which determines electrophoretic movement of charged particles under an applied electric field from the Doppler shift of scattered light, for zeta potential determination.

This series has a broad range of capabilities, including conventional static and automatic titration measurements for both size and zeta potential distributions of suspended particles in a wide range of size and concentration. The DelsaNano also can measure zeta potential of a solid surface or film.

Measuring Colloidal Particle Size Distribution by Dynamic Light-Scattering

The dynamic light-scattering method can be used to obtain particle size distributions of colloidal particles. This method is commonly used to evaluate dispersion stability. In this study, the Beckman Coulter DelsaNano, a dynamic light instrument, was used to measure particle sizes of polystyrene latex (PSL) dispersed in salts with different valences.

Particle Size Distribution of Polystyrene Latex (PSL) in Aqueous Solutions

Figure 1 shows the average particle size <d> and particle size distribution for latex (d = 115 nm; conc.: 0.01%) dispersed in aqueous solutions of 10 mM salts (monovalent: NaCl; divalent: CaCl₂; trivalent: AlCl₃). As the salt valence increased, agglomeration occurred more significantly, <d> became large and the particle size distribution broadened.

Figure 1. PSL in 10mM NaCl, CaCl₂, and AlCl₃. Image credit: Beckman Coulter

Figures 2-4 show the average particle sizes <d> and particle size distributions for the same latex dispersed in aqueous solutions with various salt concentrations (10 mM, 50 mM, 100 mM, 200 mM, 300 mM) of the above three types of salt. At high salt concentrations, <d> increased. The results show that the higher the salt concentration and the higher the salt valence, the greater the agglomeration.

Figure 2. PSL in different concentration of NaCl solution. Image credit: Beckman Coulter

Figure 3. PSL in different concentration of CaCl₂ solution. Image credit: Beckman Coulter

Figure 4. PSL in different concentration of AlCl₃ solution. Image credit: Beckman Coulter

This information has been sourced, reviewed and adapted from materials provided by Beckman Coulter, Inc. - Particle Characterization.

For more information on this source, please visit Beckman Coulter, Inc. - Particle Size Characterization.