ISO/TC 24/SC 4/WG 7 - Dynamic light scattering

This document provides practical guidance for performing and interpreting measurements using dynamic light scattering (DLS) that goes beyond the treatment of measurement artefacts in ISO 22412:2017. This document is intended to help users with experiments planning, in particular with respect to obtaining the necessary information on the sample and deciding whether DLS is the most appropriate method. It provides information on how to prepare samples in an appropriate way, verify the proper functioning of the instrument and interpret the data correctly, including ways to assess data quality. This document focuses on the practical steps required to obtain DLS results of good quality, rather than on theoretical considerations, and covers not only the measurement of solid particles, but also emulsions and bubbles.

ISO 22412:2017 specifies the application of dynamic light scattering (DLS) to the measurement of average hydrodynamic particle size and the measurement of the size distribution of mainly submicrometre-sized particles, emulsions or fine bubbles dispersed in liquids. DLS is also referred to as "quasi-elastic light scattering (QELS)" and "photon correlation spectroscopy (PCS)," although PCS actually is one of the measurement techniques. ISO 22412:2017 is applicable to the measurement of a broad range of dilute and concentrated suspensions. The principle of dynamic light scattering for a concentrated suspension is the same as for a dilute suspension. However, specific requirements for the instrument setup and specification of test sample preparation are required for concentrated suspensions. At high concentrations, particle-particle interactions and multiple light scattering can become dominant and can result in apparent particle sizes that differ between concentrated and dilute suspensions.

ISO 22412:2008 specifies a method for the application of dynamic light scattering (DLS) to the estimation of an average particle size and the measurement of the broadness of the size distribution of mainly submicrometre-sized particles or droplets dispersed in liquids. ISO 22412:2008 is applicable to the measurement of a broad range of dilute and concentrated suspensions. The principle of DLS is the same as for a dilute dispersion. However, specific requirements for the instrument set-up and specification of test sample preparation, as well as some advice on the correct interpretation of the results of measurements for concentrated dispersions, are required.