Overview
ISO 14911:1998 - Water quality: Determination of dissolved Li+, Na+, NH4+, K+, Mn2+, Ca2+, Mg2+, Sr2+ and Ba2+ using ion chromatography - specifies an ion chromatographic method for measuring dissolved cations in water and waste water. The method uses a low-capacity cation-exchange separator column and conductivity detection (with or without a suppressor). It covers typical working ranges, eluent examples, preparation of stock and mixed standards, calibration strategy and essential instrument requirements for reliable routine analysis.
Key topics and technical requirements
- Analytes: Li+, Na+, NH4+, K+, Mn2+, Ca2+, Mg2+, Sr2+, Ba2+ (dissolved fraction in drinking, surface and waste water).
- Detection: Conductivity detector (CD); suppressor devices recommended to lower eluent conductivity and improve sensitivity.
- Separator column performance: Minimum peak resolution R ≥ 1.3 for any pair of peaks under applicable conditions.
- Working ranges (example with 10 µl loop): Lithium 0.01–1 mg/L, Sodium/Ammonium/Potassium 0.1–10 mg/L, Mn/Ca/Mg/Sr 0.5–50 mg/L, Barium 1–100 mg/L. Loop size (e.g., 10 µl or 100 µl) and sample dilution adjust detection range.
- Eluents (examples): HCl/DAP, methanesulfonic acid, tartaric acid/PDA concentrate, nitric acid - chosen per column manufacturer guidance; eluents must be degassed and renewed periodically.
- Calibration and QC: Prepare 5–10 calibration solutions across the working range; follow ISO 8466-1/2 strategies for linear and non-linear calibration. Use standard-addition where necessary and perform replicate determinations and validation checks.
- Interferences & sample pretreatment: Organics (amino acids, amines), complexing agents and suspended solids can interfere or shorten column life; remove solids/organics, dilute samples as required, and verify applicability for wastewater.
- Reagents & standards: Guidance on preparation, storage (polyethylene, 4–6 °C) and stability of stock and mixed standards; attention to titre adjustments where referenced standards apply.
Applications and who uses it
- Environmental and public-health laboratories performing water quality testing for regulatory compliance and monitoring.
- Municipal water utilities and wastewater treatment plants for process control and influent/effluent monitoring.
- Contract testing laboratories and research groups needing reproducible analysis of dissolved cations by ion chromatography.
- Instrument and column manufacturers verifying system performance against standard requirements (resolution, detection, eluent compatibility).
Related standards
Normative references include ISO sampling and method standards commonly used alongside ISO 14911:
Keywords: ISO 14911:1998, water quality, ion chromatography, dissolved cations, conductivity detector, eluent, calibration, water and waste water analysis.
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