Application Help

 
Alphabetically by application:
 

Library

What is Dynamic Light Scattering?

  • Particles suspended in a liquid are subject to Brownian motion.
  • Small particles diffuse"faster".
  • Large particles diffuse "slower".
  • The time variation of the scattered intensity is analyzed by examining their auto-correlation. From this a diffusion coefficient can be derived. Please see our literature section for additional infornmation.
  • From the measured diffusion coefficient particle size is calculated.

  • A beam of laser light is focussed in the sample.
  • Particles in the scattering volume scatter light in all directions.
  • The scattered photons are measured by a photomultiplier tube
  • The Intensity appears to fluctuate randomly.
  • A digital correlator is used to compute the autocorrelation function.

  • The autocorrelation function is an exponential decay:

  • Each monodisperse population of particle sizes produces its own unique autocorrelation function - a single exponential decay.
  • Mixtures of more than one size population produce sums of exponentials.
  • Available algorithms can be used to extract "true" size distributions from complex samples - NNLS, CONTIN.

Two instruments which use this principle to determine particle size are our 90Plus bench top and our BI-200SM goniometer units. Estimates of Protein Molecular Size and Polydispersity can be obtained using this method.