Laser Diffraction Particle Size Analysis (PSA)

Laser Diffraction Particle Size Analysis
Two identical batches of catalysts (numbered 3 and 4) were placed in a reactor for differing lengths of time (Batch 4 had the longer reactor time). The laser-diffraction PSA size distribution from both batches are overlaid to show increased prevalence of smaller particles (0.1 - 10 micron equivalent spherical diameter) in Batch 4.

Particle size analysis (PSA) is an indirect, optical technique used to measure particle size distributions – by equivalent spherical diameter (D10, D50, D90) – in liquid and solid samples.

Strengths
  • Particle size measurement is not impacted by flow behavior
  • Rapid measurement
  • Minimal sample preparation
Limitations
  • Accurate interpretation requires some up-front understanding of particles’ morphology
  • Semi-quantitative
  • Not able to determine particle shape
Example Outputs

Two identical batches of catalysts (numbered 3 and 4) were placed in a reactor for differing lengths of time (Batch 4 had the longer reactor time). The laser-diffraction PSA size distribution from both batches are overlaid to show increased prevalence of smaller particles (0.1 – 10 micron equivalent spherical diameter) in Batch 4.

From: Anton Paar
Instruments Used for PSA
Anton Paar PSA 1190 LD

Anton Paar PSA 1190 LD

  • Particle Size Measuring Range: 0.1 µm to 2500 µm
  • Repeatability: < 1%
  • Particle Size Accuracy: < 3%
  • Dry Jet Dispersion (DJD) technology to prevent agglomerate formation and improve accuracy

View Instrument Spec Sheet

Sample Requirements
  • Maximum Particle Diameter: 2500 µm
  • Minimum Particle Diameter (Dry): 0.1 µm
  • Minimum Particle Diameter (Wet): 0.04 µm
How PSA Works

In a PSA measurement, an incoming laser beam is cast upon particles suspended in solution, each of which diffract photons from the incident beam. Interferences in the diffracted light generate a pattern detected with an optical sensor. This diffraction pattern can be generated within one second; making raw data collection extremely fast.

Once the pattern is recorded, it can then be analyzed using Fraunhofer or Mie theories of optics, which correlate measured intensity of the diffracted light to particle size: bigger particles produce narrower diffraction rings. This correlation allows analysts to deconstruct a dataset of 2D laser diffraction patterns into 1D intensity curves plotted as a function of particle size, yielding a volume-based size distribution for all particles in the sample.

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