Overview
EN ISO 10304-3:1997 specifies ion‑chromatographic methods for the determination of dissolved anions in aqueous samples - specifically chromate, iodide, sulfite, thiocyanate and thiosulfate. Published under ISO/TC 147 for water quality, this part of ISO 10304 is intended principally for waste water monitoring and provides procedures, detector options and working ranges to ensure repeatable, comparable results in environmental laboratories.
Key topics and technical requirements
- Scope and analytes: Procedures for iodide, thiocyanate and thiosulfate (clause 4), sulfite (clause 5) and chromate (clause 6).
- Separation principle: Liquid ion chromatography using a low‑capacity anion exchanger and aqueous eluents (salts of weak acids). Organic modifiers (e.g., 4‑hydroxybenzonitrile, methanol, acetonitrile) can improve elution and reduce peak tailing for polarizable ions.
- Detector options:
- Conductivity detector (CD) - commonly combined with suppressors to lower eluent conductivity.
- UV detector (UV) - direct or indirect absorbance (wavelengths noted in the standard).
- Amperometric detector (AD) - measures oxidation current; operating voltage depends on eluent pH.
- Performance and calibration:
- Column peak resolution minimum R = 1.3 for target analytes.
- Calibration and evaluation of linear working range required (see ISO 8466‑1 referenced). Validation checks and replicate determinations are recommended.
- Working ranges (examples from standard): typical analyte working ranges span approximately 0.05–50 mg/l (chromate) and 0.1–50 mg/l (iodide, thiocyanate, thiosulfate, sulfite) depending on detector choice.
- Reagents & eluents: Uses analytical‑grade reagents and degassed water (conductivity