Overview
ISO/TS 5973:2024 - "Laser diffraction measurements - Good practice" is a technical specification from ISO that provides practical guidance for performing laser diffraction particle size analysis. Unlike theoretical standards, this document focuses on the day‑to‑day steps needed to obtain reliable particle size distributions (PSDs) and good quality data. It covers wet and dry measurement configurations and explicitly includes solids, emulsions and bubbles, plus real‑sample variation expectations.
Key topics and requirements
- Method applicability: Guidance on determining when laser diffraction is the most appropriate technique for a given sample or measurement objective.
- Sample information & preparation: Recommended information to collect before analysis and best practices for sampling powders, suspensions, emulsions, sprays, aerosols and bubbles to reduce bias and improve representativeness.
- Instrument verification and qualification: Practical checks to confirm correct instrument functioning and to support installation, operational and performance qualification (IQ/OQ/PQ).
- Data interpretation and quality assessment: How to interpret scattering patterns, assess background stability, detect multiple scattering, and evaluate non‑smooth scattering signatures that indicate measurement issues.
- Precision and reproducibility: Procedures and definitions for repeatability, intermediate precision and reproducibility, including which measurands to monitor and when tighter or wider control limits are appropriate.
- Optical properties guidance: Considerations for coloured, porous or mixed samples and appropriate use of refractive index (Mie vs Fraunhofer considerations).
- Troubleshooting trends: Practical explanations of common trends such as dispersion, dissolution, agglomeration and random variation in repeated measurements.
- Orthogonal techniques: Recommendations to combine laser diffraction with image analysis or dynamic light scattering to validate results and resolve ambiguities.
- Validation and method transfer: Advice on method validation, qualification and inter‑laboratory transfer to ensure consistent PSD results.
Applications
ISO/TS 5973:2024 is intended for laboratories and industries that routinely characterize particle size, including:
- Pharmaceuticals (powders, suspensions, emulsions)
- Chemical and materials R&D
- Food and cosmetics quality control
- Paints, coatings and aerosols
- Environmental and aerosol monitoring
It helps ensure robust particle size distribution (PSD) measurements using laser diffraction, improving comparability and traceability of results.
Who should use this standard
- Laboratory analysts and method developers
- Quality control and R&D teams
- Instrument manufacturers and service providers
- Regulatory and accreditation bodies
Related standards
- ISO 13320 (principles and instrument evaluation for laser diffraction) - ISO/TS 5973:2024 is intended to be used in conjunction with ISO 13320 for a complete approach to laser diffraction measurement practice.