ISO 22412:2025

Overview

ISO 22412:2025 - Particle size analysis - Dynamic light scattering (DLS) specifies how to apply dynamic light scattering for measuring average hydrodynamic particle size and size distributions of mainly sub‑micrometre particles, emulsions and fine bubbles dispersed in liquids. The third edition extends applicability to both dilute and concentrated suspensions and adds multi‑angle and imaging DLS methods. The standard covers instrument requirements, sample preparation, measurement procedures, data evaluation and quality control.

Key technical topics and requirements

• Scope and definitions: clear terms for hydrodynamic diameter, polydispersity index (PI), scattering volume, count rate, reference materials and qualification concepts.
• Principle and apparatus: fundamentals of DLS measurement geometry, lasers and detectors; differences between homodyne/heterodyne modes and single vs multi‑angle setups.
• Sample preparation: guidance on concentration limits, checks for concentration suitability and recommendations for handling dilute and concentrated suspensions (Annex C).
• Measurement procedures: stepwise measurement planning, acquisition modes (autocorrelation, cross‑correlation, frequency analysis, spatial correlation) and multi‑angle/online options (Annex B).
• Data evaluation methods: correlation analysis (cumulants method), distribution algorithms (NNLS, CONTIN and others), frequency analysis, and advanced approaches such as MADLS (multi‑angle DLS), imaging DLS (IDLS, UIDLS) and polarization‑separated backscatter cross‑correlation.
• Quality assurance: system qualification, use of reference materials/CRMs, quality control checks, method precision and measurement uncertainty (Clause 10).
• Reporting and artefact guidance: required elements for test reports and annexed guidance on artefacts, interpretation and measurement planning (Annexes D and E).

Practical applications

ISO 22412:2025 is applicable where reliable sub‑micrometre particle sizing is required, including:

• Pharmaceutical formulations (suspensions, liposomes, protein aggregates)
• Nanomaterials and colloid research (R&D and characterization)
• Food and cosmetic emulsions and quality control
• Environmental and process monitoring (fine bubbles, wastewater colloids, online process control)
• Instrument validation and commercial DLS system development

Who should use this standard

• Analytical laboratories and quality control teams performing particle size analysis
• Research scientists in colloid, nanoscience and formulation development
• Instrument manufacturers and service providers for DLS systems
• Regulatory and accreditation bodies assessing measurement traceability and uncertainty

Related standards

• ISO 9276 (particle size distribution presentation)
• ISO 26824 (terminology)
• ISO 17034, ISO 33405, ISO 33401 (reference material and certification guidance)
• ISO/IEC Guide 99 (metrological traceability)

Using ISO 22412:2025 ensures standardized, reproducible DLS measurements and supports robust interpretation of hydrodynamic size and distribution data across laboratory and industrial contexts.