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Laser diffraction is a widely used particle sizing technique for materials ranging from hundreds of nanometers up to several millimeters in size. The main reasons for its success are:

  • Wide dynamic range - from submicron to the millimeter size range.
  • Rapid measurements - results generated in less than a minute.
  • Repeatability - large numbers of particles are sampled in each measurement.
  • Instant feedback - monitor and control the particle dispersion process.
  • High sample throughput - hundreds of measurements per day.
  • Calibration not necessary - easily verified using standard reference materials.
  • Well established technique - covered by ISO13320 (2009).

Principles

Laser diffraction measures particle size distributions by measuring the angular variation in intensity of light scattered as a laser beam passes through a dispersed particulate sample. Large particles scatter light at small angles relative to the laser beam and small particles scatter light at large angles, as illustrated below. The angular scattering intensity data is then analyzed to calculate the size of the particles responsible for creating the scattering pattern, using the Mie theory of light scattering. The particle size is reported as a volume equivalent sphere diameter.

Optical properties

Laser diffraction uses Mie theory of light scattering to calculate the particle size distribution, assuming a volume equivalent sphere model.

Mie theory requires knowledge of the optical properties (refractive index and imaginary component) of both the sample being measured, along with the refractive index of the dispersant. Usually the optical properties of the dispersant are relatively easy to find from published data, and many modern instruments will have in-built databases that include common dispersants. For samples where the optical properties are not known, the user can either measure them or estimate them using an iterative approach based upon the goodness of fit between the modeled data and the actual data collected for the sample.

A simplified approach is to use the Fraunhofer approximation, which does not require knowledge of the optical properties of the sample. This can provide accurate results for large particles. However it should be used with caution whenever working with samples which might have particles below 50µm or where the particles are relatively transparent.

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Caractérisation des particules par diffraction laser Classroom based training (French)

Notre formation s'adresse soit à de nouveaux utilisateurs, soit à des utilisateurs souhaitant une remise à niveau ou un approfondissement de leurs connaissances ou souhaitant développer de nouvelles applications. Aucun diplôme ...

Date:
April 8 2014
Location:
Vénissieux, Parc Club du Moulin à Vent, 33 Avenue du Dr Lévy - Bâtiment 25, Vénissieux, France, 69693
Language:
French
More details

Keywords: French Laser diffraction France Classroom based training Central Europe Time 

Mastersizer 3000 User Meeting - Chicago Classroom based training (English)

Learn More – Discover how to get the best out of your instrument with hands-on one-on-one training sessions. Share More – Share your Mastersizer experience with our user community. See More – Meet technology experts and see ...

Product:
Mastersizer 3000
Date:
May 22 2014
Location:
Particle Technology Labs, 555 Rogers St., Downers Grove, Illinois, IL, USA, 60515
Language:
English
Price:
89

Keywords: English Mastersizer 3000 Particle shape Particle size Laser diffraction USA Classroom based training Central Time 

Complete particle characterization for the modern lab - Chicago, IL Seminar (English)

Learn More – Review theory behind laser diffraction particle sizing and how to apply it successfully to your work. Explore alternative methods like particle image analysis as well. See More – Meet technology experts and see our lat...

Date:
May 21 2014
Location:
Hilton Garden Inn Schaumburg, 1191 East Woodfield Road, Schaumburg, Illinois, IL, USA, 60173
Language:
English

Keywords: English Particle shape Particle size Laser diffraction USA Seminar Central Time 

Masterclass 2: Developing wet or liquid dispersion methods using laser diffraction Webinar - Recorded (English)

This webinar will cover method development for samples dispersed in liquids. This will include a discussion of factors affecting the measurement, such as sampling and dispersion, and the relative importance of these factors in different particle size...

Date recorded:
April 3 2014
Language:
English

Keywords: English Particle size Laser diffraction Webinar - Recorded Eastern Time 

Setting pharmaceutical product specifications for particle size analysis Webinar - Recorded (English)

The end point of any particle size measurement is to provide improved product or process understanding and/or control. It order to achieve this, it is important that the size specifications selected are relevant to those products or processes. In thi...

Product:
Mastersizer range,Morphologi G3
Date recorded:
March 19 2014
Language:
English

Keywords: English Mastersizer range Morphologi G3 Particle shape Particle size Image analysis Laser diffraction Webinar - Recorded Eastern Time Pharmaceutical development 
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