SIST-TS CEN ISO/TS 21357:2023 PDF

Overview

CEN ISO/TS 21357:2023 (ISO/TS 21357:2022) defines guidance and requirements for evaluating the mean (spherical) equivalent diameter of nano‑objects (particles, droplets, bubbles) dispersed in liquids using static multiple light scattering (SMLS). The Technical Specification is intended for direct measurement of as‑received dispersions across a wide range of concentrations without mandatory dilution, enabling characterization of nanoparticles in their native state.

Key topics and requirements

• Scope and measurand: Procedures to determine the mean (spherical) equivalent diameter of nano‑objects in liquid dispersions using SMLS.
• Principle of SMLS: Measurement of transmitted or backscattered light intensity after multiple successive scattering events in a random scattering medium.
• Method applicability and limitations: Guidance on when SMLS is appropriate (including concentration effects, sample homogeneity and stability) and constraints on interpreting results (e.g., when aggregation/agglomeration or strong absorption may affect outcome).
• Apparatus and settings: Requirements for instrument setup, system settings, refractive index and volume‑fraction inputs, and procedures to verify sample homogeneity.
• Measurement procedure: Stepwise instructions covering instrument preparation, sample handling and recommended system settings to obtain reliable mean size estimates.
• Performance qualification and instrument qualification: Criteria and informative annexes that describe instrument qualification, comparative analyses, and interlaboratory study results to support method performance.
• Data recording and uncertainty: Mandatory elements to record in measurement reports and guidance on assessing measurement uncertainty for the mean equivalent diameter.
• Informative annexes: Examples and supporting materials (e.g., I and l* relationships, case studies on titanium dioxide and latex suspensions, interlaboratory comparison) that illustrate method application and interpretation.

Applications and who uses it

• Quality control and R&D: Manufacturers of nanoparticle‑containing products (paints, coatings, pharmaceuticals, cosmetics, emulsions) use SMLS to monitor mean particle size in production and storage without dilution artifacts.
• Regulatory and safety assessment: Regulators and testing laboratories assessing claims related to nanoparticle size and stability in liquid formulations.
• Analytical and contract labs: Laboratories offering characterization services where measuring the mean size of concentrated dispersions in their native state is required.
• Process monitoring: Real‑time or time‑series monitoring of aggregation/agglomeration or dissolution in dispersions (within SMLS limitations).

Related standards

• Vocabulary and definitions referenced: ISO/TS 80004‑1, 80004‑2, 80004‑4, 80004‑6 (nanotechnologies - vocabulary and nano‑object characterization).
• Cross‑references to standards addressing measurement uncertainty, optical properties, and particle characterization may be relevant in implementation.

Keywords: CEN ISO/TS 21357:2023, SMLS, static multiple light scattering, mean particle size, nano‑objects, liquid dispersions, mean equivalent particle diameter, nanoparticle characterization.