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Particle size

PARTICLE SIZE ANALYSIS IN NATIVE STATE DISPERSIONS

Particle size and its evolution are key parameters which have to be monitored and controlled to 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. TURBISCAN® is a powerful tool to measure the mean particle size in concentrated media. Thanks to the use of Static Multiple Light Scattering, 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.

Unlike most of the measurement techniques available, that require processing of the sample (pumping, dilution, stirring, centrifugation etc..), for instance: Laser Diffraction, Dynamic Light Scattering, Particle Tracking Analysis, Microscopy, Ultracentrifugation…. TURBISCAN® is the solution to analyze the samples in their native form.

Key benefits

  • No Sample dilution
  • Wide range of concentration (10-4 - 95%)
  • Wide range of size (10 nm - 1,000 microns)

How does it work?

SMLS is the only technique of particle size measurement to offer the advantage of working in concentrated media: It is well adapted for working without dilution at high concentrations (up to 95% v:v) and over a wide particle size range: 10 nm - 1 mm.

The emitted light only partially passes through the tube, most are scattered by the particles in the sample. TURBISCAN® detects the intensity of both Transmitted and Backscattered light. These intensities directly depend on the particle size (d), the concentration (Φ). Based on Mie theory it is possible to compute the mean spherical equivalent diameter.

Hydrodynamic diameter can also be calculated, thanks to the general law of migration based on Stock Equation, by measuring the migration rate of particles/droplets during sedimentation or creaming..

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Data and key features

> mean diameter

Based on the Mie theory, it is possible to compute the average spherical equivalent diameter of the particles in a concentrated media. 
This computation is based on the refractive index of particles and continuous phase, and the volume fraction of particles in the sample.

> hydrodynamic diameter

Based on the Stokes equation extended to concentrated media, it is possible to calculate the hydrodynamics mean diameter of the particles during a migration process. The faster the particles move, the smaller they are.
This computation is based on the density of the particles and continuous phase, the viscosity of the continuous phase and the particles concentration.

> Dispersibility ratio

Dispersibility (as defined by ISO 18748) is "a characteristic quantifying the ability of particles to be uniformly distributed in volume [...] and of specified size". It is a key parameter in the process for various applications (Carbon nanotubes, graphene, slurries...).

Static Multiple Light Scattering is very well adapted to measure directly the dispersibility, as it can work on concentrated samples without dilution, and without any risk to alter the dispersion state.