ISO 14403-2:2012

Overview

ISO 14403-2:2012 - Water quality - Determination of total cyanide and free cyanide using flow analysis (Part 2: continuous flow analysis, CFA) specifies a validated laboratory method for measuring cyanide in a wide range of water types (ground, drinking, surface, leachate and waste water). The standard covers automated continuous flow analysis (CFA) workflows, typical cyanide concentrations (usually 2 µg/l to 500 µg/l; the method describes a practical range of 10 µg/l to 100 µg/l) and adaptations for challenging matrices, including seawater.

Key technical topics and requirements

• Principle: On-line sample processing in a CFA manifold with separation of hydrogen cyanide (HCN) by in-line distillation (125 °C) or gas diffusion (30–40 °C), followed by photometric detection. Total cyanide is obtained after UV-B digestion at pH 3.8; free cyanide is determined with the UV lamp switched off and addition of zinc sulfate to precipitate iron-bound cyanides.
• Detection chemistry: Cyanide reacts with chloramine‑T to form cyanogen chloride, which then couples with pyridine‑4‑carboxylic acid and 1,3‑dimethylbarbituric acid to produce a red dye measured photometrically.
• Interferences & mitigation:
  • Oxidizing agents (e.g., chlorine) - neutralize with sodium thiosulfate and stabilize with ascorbic acid where appropriate.
  • Sulfide, sulfite, nitrite, carbonyl compounds and thiocyanate - require pretreatment (e.g., lead carbonate for sulfide, sulfamic acid to address nitrite).
  • High particulate or high-salt samples (>10 g/l) - filtration or dilution; consider using gas-diffusion instead of distillation.
• Reagents & standards: Analytical-grade reagents including KCN or potassium tetracyanozincate reference solutions, NaOH buffers, chloramine‑T, and color reagent components. Note toxic hazards of cyanide compounds and wastes.
• Instrumentation & setup: CFA manifold, UV digestion coil (quartz/borosilicate/PTFE), distillation or gas-diffusion module, flow photometer or-optionally-amperometric detection (see annex C). Calibration strategy and performance evaluation follow ISO guidance.

Practical applications and users

ISO 14403-2 is intended for:

• Environmental and public‑health laboratories performing routine monitoring of cyanide in water.
• Regulatory compliance testing for drinking water, surface waters, groundwater, wastewater and industrial effluents.
• Research labs and monitoring programs needing high-throughput automated cyanide analysis (large sample series). Benefits include automation, adaptability of measurement range (via dilution or flow-cell pathlength), and options for matrix-specific adaptations (seawater, high-salinity samples).

Related standards

• ISO 14403-1 (FIA method)
• ISO 3696 (Water for analytical use)
• ISO 5667-3 (Sampling - preservation/handling)
• ISO 8466-1 / ISO 8466-2 (Calibration and method evaluation)

Keywords: ISO 14403-2, continuous flow analysis, CFA, cyanide, water quality, total cyanide, free cyanide, gas diffusion, UV digestion, photometric detection, amperometric detection.