Overview
ISO 22412:2017 - "Particle size analysis - Dynamic light scattering (DLS)" defines the application of dynamic light scattering (DLS) for measuring the average hydrodynamic particle size and size distribution of mainly submicrometre particles, emulsions and fine bubbles dispersed in liquids. The standard covers both dilute and concentrated suspensions and clarifies terminology and measurement principles (also known as quasi‑elastic light scattering (QELS) or photon correlation spectroscopy (PCS)). ISO 22412:2017 replaces earlier editions and establishes requirements for apparatus, sample preparation, measurement procedure, data evaluation and quality control.
Key topics and technical requirements
- Principle and scope: DLS probes Brownian motion to infer particle size using the Stokes–Einstein relation; applicable mainly to submicrometre particles and typically not suitable for very large settling particles.
- Apparatus and optical setup: Requirements for instrument configurations (homodyne/heterodyne modes, detection angles, laser source) and special setup considerations for concentrated suspensions where multiple scattering and particle interactions occur.
- Sample preparation: Guidance on concentration limits, checks for suitability, and recommended preparation steps to avoid artefacts (see Annex D).
- Measurement procedure: Standardized steps for acquiring raw data (autocorrelation, cross‑correlation, frequency analysis) and considerations for inline/online measurements (Annex C).
- Data evaluation: Algorithms and analysis methods such as the cumulants method (z‑average), distribution calculation methods (NNLS, CONTIN and other inversion algorithms) and frequency‑domain approaches; definitions of polydispersity index (PI) and average hydrodynamic diameter.
- System qualification and quality control: Requirements for instrument qualification, use of reference or certified reference materials, method precision and reporting of measurement uncertainty.
- Guidance on artefacts: Identification and mitigation of measurement artefacts (multiple scattering, fluorescence, sedimentation) described in informative annexes.
Practical applications and who uses ISO 22412
ISO 22412:2017 is used by:
- Analytical and research laboratories performing particle size analysis of nanoparticles, colloids, emulsions and foams.
- Quality control teams in pharmaceuticals, biotechnology, cosmetics, food and materials manufacturing for routine DLS measurements.
- Instrument manufacturers and validation engineers for system qualification and performance testing.
- Researchers in nanotechnology and colloid science requiring standardized reporting of z‑average, PI and size distributions.
Practical benefits include reproducible DLS methods, harmonized reporting, and clearer interpretation of results across dilute and concentrated systems.
Related standards
- ISO 9276‑1: Graphical representation of particle size results
- ISO 9276‑2: Calculation of average particle sizes and moments from distributions
Keywords: ISO 22412, dynamic light scattering, DLS, particle size analysis, hydrodynamic diameter, size distribution, photon correlation spectroscopy, polydispersity index, sample preparation, quality control.