The ISO/TS 21357 outlines how to evaluate the mean equivalent particle diameter of liquid dispersions using the static multiple light scattering method (SMLS). The software of the device should be able to calculate the mean equivalent particle diameter using the Mie theory.

ISO/TS 21357: Application and Use

Dispersions that contain nanoparticles in liquid are used in many industries. To measure the mean equivalent particle size of such dispersions, the static multiple light scattering method may be used. Its advantage over other methods is that the sample can be analyzed in its original concentration and without a complex sample preparation. Please note that this method cannot measure the particle size distribution, only the mean equivalent particle diameter.

ISO/TS 21357: Experimentation

Apparatus

To carry out the static multiple light scattering method (SMLS), the dispersion sample is filled into a round vessel and placed in a measuring tower. The measuring system contains light sources and a light detector. This enables changes in the transmitted and backscattered light to be determined in terms of position and time. The software of the device should be able to calculate the mean equivalent particle diameter using the Mie theory.

The MS 20 Dispersion Stability Analysis System from DataPhysics Instruments can be used to conduct the static multiple light scattering method (SMLS) to calculate the mean equivalent particle diameter using the Mie theory.

Procedure

The device should be set up according to the manufacturers specifications. The sample can be analyzed without being diluted. The concentration should be uniform. To achieve that, the sample might be shaken gently before introduced into the measurement device. The measurement should follow the guidelines of the standard ISO 14488: 'Particulate materials — Sampling and sample splitting for the determination of particulate properties'.

The ISO/TS 21357 is in use since 2022 and last reviewed in 2025.

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