Dynamic light scattering

Dynamic Light Scattering

Dynamic Light Scattering (DLS), also known as Photon Correlation Spectroscopy (PCS) and Quasi Elastic Light Scattering (QELS), is one of the most widely used particle sizing distribution techniques for sub-micron material. DLS operates by observing fluctuations in light scattered by suspended sub-micron material. These fluctuations are relative to the Brownian motion of the particles, which is then used to generate an average particle size. The final result is reported on an intensity-weighted hydrodynamic spherical equivalent diameter basis along with the polydispersity/width. Samples with broader distributions (higher polydispersity) may not be appropriate for this technique.

Particle Size by DLS is recognized by numerous standards and guidance agencies, including the ISO, ASTM, USP, EP, and JP. This technique’s focus on sub-micron material makes it a good choice for evaluating nanomaterials.

A wide variety of sample types can be analyzed by DLS, including active pharmaceuticals (APIs), emulsion droplets, exosomes, liposomes, virosomes, and other nanomaterials that are safety concerns. Common applications include QA/QC batch testing, general survey screening measurements, stability studies, and comparative studies.

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Advantages

  • Widely used particle sizing distribution technique
  • Reports on an intensity basis
  • Available for aqueous and non-aqueous suspensions
  • Broad Detection Range; 1 nanometer to 1 micron

Considerations

  • Ensemble technique with lower resolution
  • Viscosity no higher than 10 cP for the sample
  • Suspension must exhibit some turbidity for the best analysis
  • Heterogenous material cannot be distinguished

Sample Requirements

Ideal sample amount is 1 gram for solid samples, especially for new material to allow for the determination of adequate preparation and instrument settings.

For liquid samples, the preferred amount is 20 mL of at least 1% concentration and less than 10 cPs.

The above sample quantities are preferred. If sample availability is further limited, please contact us to share specifics about your sample and options for suitable sample quantities.

 

 

Detection Range

PTL’s Dynamic Light Scattering Department can measure particulate from approximately 1 nanometer (nm) up to 1 micrometer (µm).

Data Reported

Typically, DLS results are reported on an Intensity basis using Z-Average along with Polydispersity Index (PDI).  Other formats are available upon request.

Instrumentation

Particle Technology Labs uses the Malvern Panalytical Zetasizer Nano for DLS testing.

Malvern Panalytical Zetasizer Nano

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