Overview
EN ISO 10304-4:2022 (CEN endorsement of ISO 10304-4:2022) specifies a standardized ion‑chromatographic method for the determination of dissolved anions chlorate, chloride and chlorite in waters with low contamination (for example drinking water, raw water and swimming‑pool water). The method uses ion chromatography with a low‑capacity anion‑exchange separator column and common detectors (conductivity, UV, amperometric). This edition updates and replaces earlier versions and is part of the ISO 10304 series on dissolved anions.
Key topics and technical requirements
- Scope and intent: Analysis of chlorate, chloride and chlorite in low‑contaminant waters. Method description is general due to diversity of instrument assemblies.
- Separation principle: Liquid chromatography of ions on a low‑capacity anion exchanger (separator column).
- Detectors and detection conditions:
- Conductivity detector (CD) commonly used for chlorate and chloride.
- UV detector for chlorite (λ = 207–220 nm).
- Amperometric detector (AD) for chlorite (operating potential ~0.4–1.0 V).
- Working ranges (typical):
- Chlorate: 0.03 to 10 mg/L (CD)
- Chloride: 0.1 to 50 mg/L (CD)
- Chlorite: 0.1 to 1 mg/L (UV 207–220 nm) or 0.01 to 1 mg/L (AD, careful method control)
- Interferences and sample pretreatment:
- Organic acids, disinfection by‑products, dissolved organics and particulates can interfere and shorten column life; filtration and cleanup are required.
- Other anions (fluoride, carbonate, nitrite, nitrate, bromide, high chloride) can cross‑interfere; Table values in the standard indicate typical cross‑sensitivity ratios (e.g., 1 part chlorate : 50 parts bromide can affect CD detection).
- Elevated chloride/bromide may require removal with special ion exchangers or dilution (Clause 9.2).
- Quality/control: Requirements for separator column performance, calibration (ISO 8466‑1 referenced), calibration validity checks, and expression of results. Tests must be performed by qualified personnel following laboratory safety practices.
Applications
- Routine and compliance testing of drinking water, raw water sources, swimming pools and similar low‑contamination matrices.
- Monitoring of disinfection by‑products (formation of chlorite/chlorate during treatments such as chlorine dioxide).
- Use by environmental testing laboratories, water utilities, regulators and manufacturers of analytical equipment and consumables.
Who should use this standard
- Water and environmental laboratories performing ion chromatography
- Public health and regulatory agencies setting monitoring programs
- Water treatment operators and consultants assessing disinfection by‑products
- Instrument and column manufacturers aligning products with standardized performance criteria
Related standards and references
- ISO 8466‑1: Calibration and evaluation of analytical methods - Part 1: Linear calibration function
- Other parts of ISO 10304 series (see ISO website and Bibliography in the standard)