Overview
ISO/TR 19997:2018 - "Guidelines for good practices in zeta-potential measurement" is a technical report from ISO that provides practical guidance for preparing samples and conducting zeta-potential measurements. It does not prescribe a complete measurement procedure but offers best-practice instructions useful when performing zeta-potential tests in accordance with ISO 13099‑1 and ISO 13099‑2. The guidance targets optically‑based electrophoretic mobility and electroacoustic methods used to assess colloidal and particulate systems.
Key topics and requirements
- Scope and intent: Guidance for product design, formulation optimization and quality control where zeta-potential is used to assess electrostatic interactions and dispersion stability.
- Principle: Zeta-potential is the electric potential at the shear plane and is derived from measured electrophoretic mobility or electroacoustic response; it depends on both particle and medium properties.
- Sample preparation: Emphasizes that dilution can alter the dispersion medium and particle surface - recommending equilibrium dilution (use of the original liquid or "mother liquor") or dialysis where applicable to preserve ionic composition. Special care to avoid solvent shock, dissolution, or surface changes during preparation.
- Sampling and inspection: Samples must be representative, well dispersed, and free of sedimentation during measurement; document handling and diluent preparation in reports. Disposable, chemically compatible labware is preferred to reduce contamination.
- Measurement uncertainty & common error sources: Lists key error contributors such as carryover contamination, inappropriate preparation or liquid medium, incorrect operator entries, air bubbles, carbon dioxide effects, inappropriate theoretical models for converting mobility to zeta, and electric-field effects on sensitive samples.
- Non‑polar media: Informative annex (Annex A) addresses zeta-potential measurement considerations for particles in non-polar liquids.
Practical applications & users
ISO/TR 19997:2018 is useful for:
- Laboratory analysts and quality-control teams performing zeta-potential checks during manufacturing or R&D.
- Formulation scientists and product developers optimizing colloidal stability (e.g., paints, inks, pharmaceuticals, emulsions, nanomaterials).
- Researchers conducting comparative studies of surface adsorption, isoelectric points (IEP), or electrostatic stabilization.
Practical outcomes include improved reproducibility, reduced artefacts from sample handling, and better correlation between zeta-potential and stability indicators (size distribution, turbidity, viscosity).
Related standards
- ISO 13099‑1 / ISO 13099‑2 - Methods for converting measured electrophoretic mobility or electroacoustic signals into zeta-potential; ISO/TR 19997 complements these standards by addressing good practices in sample handling and measurement setup.
Keywords: ISO/TR 19997:2018, zeta-potential, sample preparation, electrophoretic mobility, electroacoustic, colloidal stability, particle characterization, ISO 13099.