Overview
ISO/TS 24672:2023 - Nanotechnologies: Guidance on the measurement of nanoparticle number concentration provides a practical, non-prescriptive overview of established methods for determining nanoparticle number concentration in liquid dispersions and aerosols. The Technical Specification compares ensemble measurement techniques and particle-counting methods, discusses sample preparation, and outlines advantages, limitations and sources of uncertainty for each approach. It is intended to help users select appropriate measurement methods for research, quality control and regulatory support.
Key topics
- Scope and measurand: Definition and importance of nanoparticle number concentration as the count of particles per unit volume (or mass) and its role in toxicology and product quality.
- Technique families:
- Ensemble techniques: DCS (differential centrifugal sedimentation), MDLS (multi-angle dynamic light scattering), SAXS (small-angle X-ray scattering), UV‑vis spectroscopy.
- Particle counting techniques: PTA (particle tracking analysis), RPS (resistive pulse sensing), spICP‑MS (single particle ICP‑MS), CPC (condensation particle counter), DMAS (differential mobility analysing system).
- Comparison and selection criteria: Guidance on choosing a technique based on particle type, size distribution, concentration range, required accuracy and precision, matrix (liquid vs aerosol), and practical constraints.
- Sample preparation: Considerations for suspensions (dispersion, dilution, avoidance of agglomeration/contamination) and aerosol sampling requirements.
- Uncertainty and limitations: Discussion of common uncertainty sources for each method and practical mitigation strategies.
- Units and reporting: Guidance on units for nanoparticle number concentration and recommended reporting practices to support comparability.
Applications and users
ISO/TS 24672:2023 is useful for:
- Analytical laboratories validating or selecting methods for particle counts.
- Nanomaterials manufacturers implementing in-process or release quality control.
- Regulatory and safety assessors using number concentration as an exposure or hazard metric in toxicology.
- Research groups developing or comparing nanoparticle measurement protocols.
- Environmental and aerosol scientists measuring airborne nanoparticle concentrations.
Practical benefits include improved method selection, clearer reporting, better comparability across studies, and support for product quality assurance and safety assessments.
Related standards
This Technical Specification was prepared by ISO/TC 229 (Nanotechnologies) and complements other ISO nanotechnology guidance. For definitive method descriptions, test methods, or formal measurement standards, consult ISO and national standards bodies (www.iso.org or your national member body) to obtain the full ISO/TS 24672:2023 text and associated nanotechnology standards.