Overview
ISO 10304-4:2022 - Water quality - Determination of dissolved anions by liquid chromatography of ions - Part 4 - specifies a validated ion-chromatographic method for measuring chlorate, chloride and chlorite in low-contamination waters (e.g., drinking water, raw water, swimming pool water). The standard updates and replaces the 1997 edition and defines procedural principles, required reagents/eluents, detector options and quality checks suited to ion chromatography (IC) workflows.
Key topics and technical requirements
- Analytes and working ranges: Typical working ranges given in the standard include chlorate (≈0.03–10 mg/L by conductivity detection), chloride (ranges up to tens of mg/L by conductivity) and chlorite (UV detection ≈0.1–1 mg/L; amperometric detection ≈0.01–1 mg/L).
- Separation principle: Liquid chromatographic separation using a low-capacity anion-exchange column and aqueous eluents (carbonate/bicarbonate or hydroxide-based) with appropriate low conductivity for CD or with suppression.
- Detection methods: Conductivity detector (CD, with/without suppressor), UV detector (207–220 nm for chlorite), and amperometric detector (AD, oxidation current for chlorite at 0.4–1.0 V).
- Eluent and reagent guidance: Eluents must be degassed and low in background conductivity. An example sodium carbonate/sodium hydrogencarbonate eluent and preparation/storage notes are provided (store eluents in amber glass, renew regularly). Stock solutions (ρ = 1 000 mg/L) and preparation hints (e.g., add NaOH; chlorite stock verified iodometrically per ISO 10530) are specified.
- Interferences and pre‑treatment: Organic acids, disinfection by-products, fluoride, nitrate, nitrite, bromide and high chloride loads can interfere. The standard requires filtration/particle removal, dilution or ion-exchange clean-up (special exchangers to remove chloride/bromide) where needed.
- Quality control: Calibration (including standard addition if required), calibration validation, replicate determinations and column resolution checks are mandatory. Qualified laboratory personnel and appropriate safety practices are emphasized.
Practical applications and users
ISO 10304-4:2022 is intended for:
- Drinking water laboratories and municipal water utilities monitoring disinfection by-products and anion profiles.
- Environmental testing labs performing routine compliance testing of raw and treated waters, and swimming pool water monitoring.
- Instrument and column manufacturers and method developers needing specifications for IC method performance and eluents.
- Research groups studying formation of chlorite/chlorate during water disinfection processes.
Use cases include regulatory compliance testing, process control of disinfection, verification of treatment effectiveness, and research into anion formation pathways.
Related standards
- ISO 10304 (series) - other parts cover different anions and techniques.
- ISO 8466-1 - calibration and evaluation of analytical methods (linear calibration function).
- ISO 10530 - iodometric determination of chlorite (used for chlorite stock solution verification).
Keywords: ISO 10304-4:2022, water quality, ion chromatography, chlorate, chlorite, chloride, drinking water testing, conductivity detector, amperometric detector, UV detection, eluents, sample pre-treatment.
Open preview (PDF)Water quality — Determination of dissolved anions by liquid chromatography of ions — Part 4: Determination of chlorate, chloride and chlorite in water with low contamination