Professional Detailing2 min read

Viscosity Inputs in DLS: A Sample Setting Can Change the Size Result

A dynamic light scattering result depends on information about the liquid surrounding the particles, including viscosity. Using an inappropriate input can affect the calculated size even when the instrument completes the measurement successfully.

Updated · NANOLAB Knowledge

The key distinction

Malvern Panalytical explains the relationship between diffusion, viscosity and hydrodynamic size. The practical purchasing issue is traceability: the report should identify the dispersant and relevant measurement conditions. A software default is not evidence that the chosen value represents a diluted or mixed sample accurately.

Practical checks

  1. Ask the laboratory to identify the dispersant and viscosity basis used in the analysis.
  2. Record the sample preparation and measurement temperature.
  3. Resolve unexplained setting differences before comparing a new report with an older acceptance result.

Example

Illustrative example: two laboratories assess samples prepared with different liquid mixtures. Their reports list particle sizes without documenting the viscosity input. Before concluding that the batches differ, the buyer asks for the missing preparation and analysis details and requests a technically appropriate comparison.

Scope and limits

Do not modify laboratory settings merely to obtain an expected answer. This guide does not prescribe a viscosity value for any NANOLAB product or ingredient. The laboratory should select and justify the method conditions, including whether the sample is suitable for the proposed measurement.

Related guidance

Technical references: Malvern Panalytical: Viscosity requirements for DLS. These sources describe their stated methods or products; they do not certify NANOLAB products or establish compatibility with an unlisted surface.

Ask NANOLAB about the exact product and intended use. Use the current product documentation for formulation-specific instructions.

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Plan a colour-change assessment for nano coatings with matched samples, consistent lighting and a clear distinction between visual observation and instrument data.

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Dynamic light scattering reports size through particle motion in a liquid. That hydrodynamic measurement need not match a dimension measured from an image of a prepared particle sample. A difference requires interpretation before either result is rejected.