Particle size

Particle size and its evolution are key parameters to monitor and characterize formulation stability and aging over time. Because particles or droplets are in weak equilibrium within the liquid phase, it is important to analyze their dispersion state in the native form.

Thanks to the use of Static Multiple Light Scattering (SMLS), no dilution or sample stress are required and the samples are analyzed in their original form. Actual dispersion state, such as the presence of agglomerates or flocs, can be rapidly and precisely identified and measured, without altering the real particle size.

Static Multiple Light Scattering (SMLS) also contributes to efficient work in concentrated media, since it is well adapted for dispersions, working without dilution at high concentrations (up to 95% v/v) and over a wide particle size range (10nm – 1mm).

  • No Sample

  • Wide range of concentration (10-4 - 95%)

  • Wide range of size (10 nm - 1,000 microns)

Schematic representation of multiple light scattering principle


From Backscattering or Transmission intensity measurement it is possible to calculate the Mean Particle Equivalent Diameter using the equations below:

IBS = backscattered light intensity
IT= transmitted light intensity
l*= transport mean free path
l= mean free path
g = asymmetry factor
Qe = extinction efficiency factor
¬φ = volume fraction =
D = mean equivalent particle diameter
N = refractive index
T0 = light flux transmitted by the continuous phase


Turbiscan particle size measurement is compliant with ISO TS 21357:2022 “Nanotechnologies — Evaluation of the mean size of nano-objects in liquid dispersions by static multiple light scattering (SMLS)”

Turbiscan offers the possibility to calculate the hydrodynamics mean diameter of the particles during a migration process thanks to the general law of sedimentation.