Dynamic light scattering is a method to measure the translational diffusion coefficient (D) of small particles in solution. Diffusion of small particles (up to a few microns) in a fluid at macroscopic equilibrium is the result of Brownian motion: random fluctuations due to the constant collision of particles with the solvent molecules surrounding them. Using on the Stokes-Einstein equation, the hydrodynamic radius rH of the solvated particles can be determined if the particle’s diffusion coefficient is known, along with the solvent temperature and viscosity.

In addition to the solution’s temperature and viscosity, how particles diffuse in a solvent is also dependent upon the particle’s molecular properties, such as size or shape, as well as the solution’s ionic strength. 

In PR.Panta Control, the diffusion coefficient of particles in a sample is obtained by fitting the autocorrelation function with suitable algorithms. Using solvent viscosity set by the user and the set temperature of the samples, the software automatically calculates the rH. The results are reported both as an average radius of all particles in solution as determined via the cumulant analysis and a distribution of radii as determined via the size distribution or regularization analysis.