Overview
ISO 17690:2015 specifies a validated analytical method for the determination of available free cyanide (pH 6) in water using flow injection analysis (FIA) combined with gas-diffusion and amperometric detection. The method applies to a wide range of waters - ground, drinking, surface, leachate, waste water and metallurgical processing waste water - for cyanide concentrations nominally from 5 µg/L to 500 µg/L (expressed as CN− in the undiluted sample). The standard describes sample handling, reagent preparation, instrumentation setup and calibration, and safety and interference controls.
Key Topics
- Analytical principle: sample injected in an FIA manifold, acidified to pH 6, HCN diffuses through a hydrophobic gas-diffusion membrane into an alkaline acceptor stream; CN− is measured amperometrically at a silver working electrode (Eapp = 0.0 V vs. reference).
- Measurement ranges: two recommended concentration ranges are described (5–50 µg/L and 50–500 µg/L); range can be adjusted by changing operating conditions (e.g., injection volume).
- Reagents & standards: specifications for NaOH acceptor solutions, KCN primary standards (including preparation and stability), potassium tetracyanozincate alternative, calibration solutions and electrode stabilization solutions.
- Calibration & performance: procedures for preparing multiple calibration points, checking recovery rates, electrode stabilization and data processing with instrument software.
- Interferences & treatments:
- Oxidizing agents: detect with acidified KI/starch paper; recommended treatment with powdered sodium arsenite when present.
- Sulfide: detect with lead acetate paper; treat with powdered lead carbonate and immediate filtration to prevent conversion of cyanide to thiocyanate.
- Quality & safety: requirements for laboratory water (ISO 3696), sampling and preservation (ISO 5667-3), and warnings on cyanide toxicity and waste disposal.
Applications
ISO 17690:2015 is intended for:
- Environmental and regulatory laboratories performing routine monitoring of cyanide in water.
- Water utilities and drinking-water testing labs assessing cyanide compliance.
- Mining, metallurgical and industrial process laboratories monitoring cyanide in process effluents and waste streams.
- Contract testing and research labs needing a high-throughput FIA method with gas-diffusion and amperometric detection.
This method is valuable where rapid, automated analysis of many samples is required and where detection within the µg/L range is needed.
Related Standards
- ISO 3696 - Water for analytical laboratory use
- ISO 5667-3 - Sampling: preservation and handling of water samples
- ISO 8466-1 / ISO 8466-2 - Calibration and evaluation of analytical methods
- ISO 2080 and ISO 14403 - referenced for definitions and comparisons of cyanide fractions
Keywords: ISO 17690:2015, available free cyanide, flow injection analysis, FIA, gas-diffusion, amperometric detection, water quality, cyanide determination, pH 6, cyanide monitoring.
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