Dynamic Light Scattering Particle Analyzer: Principles and Uses

Dynamic Light Scattering (DLS), also known as laser light scattering, is a technique used to measure the size of small particles (such as proteins, nanoparticles, polymers, or lipid vesicles) in a solution or suspension. 

 

DLS is based on analyzing the fluctuations in the scattered light intensity of particles in a solution over time. When a laser beam is shone on a sample, the particles in the sample scatter light. As the particles continuously undergo Brownian motion (i.e., random movement) in the solution, the phase and intensity of the scattered light from each particle change over time. These time-dependent scattered lights cause an interference effect, leading to fluctuations in the light intensity received on the detector. These fluctuations change with the size of the particles: larger particles fluctuate slower, while smaller particles fluctuate faster.

 

The autocorrelation function is obtained by measuring the time correlation of light intensity. The autocorrelation function describes the similarity of changes in scattered light intensity at different time intervals. Using an appropriate mathematical model (such as the Perrin equation), the diffusion coefficient of the particles is extracted from the autocorrelation function, and the hydrodynamic diameter of the particles is calculated.

 

DLS can provide the distribution of particle sizes in a solution. It is a non-invasive, fast method that usually does not require a large amount of sample. However, it should be noted that DLS may not be the best choice for very heterogeneous samples because its resolution may be limited.