Overview
ISO 13099-2:2012, "Colloidal systems - Methods for zeta‑potential determination - Part 2: Optical methods," defines standardized optical procedures to measure electrophoretic mobility of particles in liquids and to derive zeta‑potential using established theoretical models (see ISO 13099‑1 for theory). This part covers two primary optical techniques: video microscopy (microelectrophoresis) and electrophoretic light‑scattering (ELS), specifying measurement principles, cell design considerations, signal processing and operational procedures.
Key topics and technical requirements
- Measurement methods
- Video microscopy / microelectrophoresis: direct particle tracking using bright‑ or dark‑field illumination and CCD/video capture to determine particle velocity under an applied electric field.
- Electrophoretic light‑scattering (ELS): Doppler‑based ensemble method where frequency shifts of scattered coherent light yield electrophoretic mobility distributions.
- Cell design and optics
- Requirements for cells that hold samples, apply a stable, homogeneous electric field, and provide optical access; designs may be capillary or cuvette‑type.
- Differences between reference‑beam and cross‑beam optical arrangements for ELS.
- Signal processing and data analysis
- Extraction of Doppler shifts, frequency power spectra and mobility distributions; procedures to convert mobility into zeta‑potential using models given in ISO 13099‑1.
- Operational procedures and quality assurance
- Requirements for sample preparation, measurement zones, cell constants or calibration, verification, and reporting.
- Identification and mitigation of sources of measurement error, including electroosmosis, thermal convection, particle concentration effects and optical alignment.
- Ancillary guidance
- Annex on electroosmosis within capillary cells and normative references for terminology and theory.
Practical applications and users
ISO 13099-2 is intended for laboratories, instrument manufacturers and researchers involved in:
- Colloid and surface chemistry characterization
- Formulation and stability testing of paints, coatings, inks, cosmetics and pharmaceuticals
- Nanomaterials characterization and quality control
- Environmental and wastewater particle analysis
- R&D groups developing zeta‑potential measurement instruments
By standardizing optical measurement methods (video microscopy and ELS), ISO 13099‑2 improves comparability, reproducibility and traceability of electrophoretic mobility and zeta‑potential data.
Related standards
- ISO 13099‑1 - essential companion document covering theoretical models to convert electrophoretic mobility into zeta‑potential.
- ISO 13099 series (other parts under development, e.g., acoustic methods)
Keywords: ISO 13099‑2, zeta‑potential, electrophoretic mobility, electrophoretic light scattering, video microscopy, colloidal systems, optical methods.