Overview
ISO 16588:2002 - "Water quality - Determination of six complexing agents - Gas‑chromatographic method" specifies a validated GC-based procedure for quantifying six water‑soluble organic complexing agents in drinking, ground, surface and waste water. The method covers EDTA, NTA, DTPA, MGDA, β‑ADA and 1,3‑PDTA in the concentration range 0.5 µg/L to 200 µg/L (using 50–100 mL sample volumes). For high‑matrix waste waters, smaller sample volumes (e.g., 5–10 mL) are recommended to reduce matrix effects.
Keywords: ISO 16588, water quality, complexing agents, gas‑chromatographic method, EDTA, NTA, DTPA.
Key topics and technical requirements
- Scope & analytes: Determines six named complexing agents; other similar compounds may be analysed if they behave similarly during pretreatment and GC.
- Principle: Samples are stabilized with formaldehyde, evaporated to dryness, acidified, esterified to n‑propyl/iso‑propyl or n‑butyl esters, extracted with n‑hexane and analysed by gas chromatography with a nitrogen‑sensitive detector (NPD) or mass spectrometer (MS).
- Analytical range & volumes: 0.5–200 µg/L for 50–100 mL; reduce volume for high DOC or high salt matrices.
- Sample stabilization & storage: Add formaldehyde (1:100) immediately after sampling; store in the dark at ~4 °C and analyse within one month.
- Interferences & limitations:
- Metal complexes are generally broken down (except bismuth - losses possible >100 µg/L).
- High salt (>2 g/L NaCl) complicates complete evaporation - dilute or use smaller volumes.
- Ca2+ >200 mg/L can cause EDTA losses.
- Reagents & equipment: Esterification reagent (alcohol + acetyl chloride), internal standard (1,2‑PDTA), nitrile or chlorinated control standards, fused‑silica capillary columns, GC‑NPD or GC‑MS, and controlled heating at (90 ± 3) °C (30 min for butyl esters, ~3 h for propyl esters).
- Quality control: Use calibration stock solutions, internal standards and control standards; optimize GC conditions and verify identity by retention time (and MS spectra if available).
Applications and users
ISO 16588 is aimed at:
- Environmental and water quality laboratories
- Drinking water utilities and groundwater monitoring programs
- Wastewater treatment monitoring and industrial discharge testing
- Regulatory agencies and research groups assessing chelating agents (EDTA, NTA, DTPA, MGDA, β‑ADA, 1,3‑PDTA)
The method supports compliance monitoring, pollution source identification and process control where accurate determination of organic complexing agents is required.
Related standards
For implementation, follow ISO 16588’s full procedural details and safety precautions and verify any additional national regulatory requirements.
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