Laser Diffraction


Laser diffraction is used for the determination of particle size distribution

Laser diffraction is used for the determination of particle size distribution (PSD).  

The particle size distribution measured by laser diffraction is helpful for:

  1. Detection of batch-to-batch variations
  2. Test the influence of production changes on the particles
  3. Study if the PSD is a critical quality attribute for the manufacturing process
  4. Investigate the effect of PSD on dissolution and bioavailability
  5. Investigation of PSD stability during shelf life
  6. Detection of agglomerates and study the strength of agglomerates
  7. The PSD will always be the utmost critical attribute for the dry powder inhalation  (DPI) products
  8. Control the content uniformity of formulations, especially for the low drug load formulations

For Material Experts: 

Instrument and measuring principle, laser diffraction‚ÄĮ

By laser diffraction analysis, it is possible to measure particles sizes between 0.01 and 3500 ¬Ķm. The sample is dispersed in either air or a suitable liquid media. The laser passes through the dispersion media and is diffracted by the particles. The diffraction light pattern (He-Ne & Krypton laser) is dependent on the particle size. The laser diffraction pattern is measured and correlated to the particle size distribution based on Fraunhofer or Mie theory. The use of Mie theory presupposes knowledge of the light refractive index of the particles and the dispersion media and the imaginary part of the refractive index of the particles. Particle Analytical can determine these refractive index¬†parameters.

The laser diffraction instrument applied by Particle Analytical (Malvern Mastersizer 3000 and 2000) has a flow-through cell for dispersion of particles in liquid media or a dry dispenser for dispersion of particles in the air. Wet dispersion presupposes that the particles are insoluble in the liquid. Therefore method development is required. We typically offer either a simple non-GMP suitability screening or a full-length GMP method development.

InstrumentsMalvern Mastersizer 2000, 3000
USP/Ph. Eur.USP 429/Ph. Eur. 2.9.31
Dispersion unitsHydro2000SM, Hydro2000S and Scirocco2000 from Malvern, HydroMV, Aero
Dispersion mediaLiquid or air
ParametersSonication, stirring speed (liquid) feeding rate, pressure (air)
Measuring range0.01-3500, 0.02- 2000 ¬Ķm (liquid) 0.1-3500, 0.1-2000 ¬Ķm (air)
Sample amount10-500 mg (liquid) 0.5-10 g (air)

Consult our Experts


Dr. Changyong Lu
QC Chemist

Dr. Anna Shevchenko
Principal Scientist


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