Overview
ISO 17380:2013 - "Soil quality - Determination of total cyanide and easily‑liberatable cyanide - Continuous‑flow analysis method" defines an automated, photometric procedure for measuring total cyanide and easily‑liberatable cyanide in soil. The method applies to all soil types with cyanide contents above 1 mg/kg (dry matter) and uses automated distillation coupled with continuous‑flow analysis (CFA) and photometric detection to deliver high‑throughput, reproducible results.
Key topics and technical requirements
- Sample extraction: Soil is extracted with 2.5 mol/L NaOH for 16 h, then diluted 100× prior to analysis. Results are reported as cyanide ion on a dry‑matter basis.
- Total cyanide determination: Complex cyanide is decomposed in a continuous flow after addition of a citric‑acid buffer (initial pH 3.8) and UV irradiation (UV‑B lamp and borosilicate coil). Hydrogen cyanide is separated by in‑line distillation (heating bath 125 °C ± 2 °C) and measured photometrically.
- Easily‑liberatable cyanide: Prior to distillation, zinc sulfate is added to precipitate iron cyanide complexes; distillation and photometric detection follow the same CFA route.
- Photometric reaction: Cyanide reacts with chloramine‑T, then with pyridine‑4‑carboxylic acid and 1,3‑dimethylbarbituric acid to give a purple colour measured at 606 nm (600 ±10 nm with filter).
- Interferences & limits: The method is valid above 1 mg/kg; sulfide > 40 mg/kg can interfere (split peaks / slow detector response) and may require sample dilution. Thiocyanate and many organic cyanides are not measured; some metal cyanide complexes (Co, Au, Pd, Pt) are only partially decomposed.
- Instrumentation & reagents: Requires a CFA/automated distillation system, UV‑B lamp, borosilicate decomposition coil, flow cell photometer, and specified reagents and buffers. The standard includes details on reagents, calibration, precision, recovery (Annex A), apparatus guidance (Annex B), and an alternative buffer (Annex C).
- Safety: Cyanide solutions are highly toxic - follow appropriate handling and disposal precautions.
Applications and users
ISO 17380:2013 is intended for:
- Environmental and analytical laboratories performing routine soil cyanide testing
- Mining and metallurgical operations (e.g., gold processing) monitoring cyanide in tailings and soils
- Soil remediation and risk‑assessment consultancies
- Regulatory agencies and compliance testing programs
- Research laboratories studying cyanide speciation in soil
The CFA approach is especially useful where high sample throughput and automation are required.
Related standards
Keywords: ISO 17380:2013, soil quality, total cyanide, easily‑liberatable cyanide, continuous‑flow analysis, automated distillation, photometric determination, cyanide in soil.
Open preview (PDF)Soil quality — Determination of total cyanide and easily liberatable cyanide — Continuous-flow analysis method
