Overview
ISO 11262:2011 - Soil quality: Determination of total cyanide specifies manual laboratory procedures for measuring total cyanide in soil. The standard is applicable to as‑received (field‑moist) soils and validates a direct liberation method using orthophosphoric acid (normative). An alternative alkaline extraction with sodium hydroxide followed by liberation is described in Annex B (informative). The liberated hydrogen cyanide is quantified by either a photometric method or a titrimetric method.
Key topics and requirements
- Scope and sample type: Methods apply to all soil types, analyzed on an as‑received basis.
- Liberation procedures:
- Direct liberation using orthophosphoric acid (validated normative method).
- Alkaline extraction with NaOH and subsequent liberation (informative, Annex B).
- Detection methods:
- Photometric method - cyanide reacts via chloramine‑T → cyanogen chloride → coloured complex (measured at 606 nm). Lower limit ~0.5 mg/kg (as‑received).
- Titrimetric method - titration with AgNO3 using 5-(4-dimethylaminobenzylidene)rhodanine indicator. Lower limit ~10 mg/kg (as‑received).
- Note: Alkaline extraction increases lower limits (photometric ~1 mg/kg, titrimetric ~30 mg/kg).
- Reagents and apparatus: Specifies analytical‑grade reagents (orthophosphoric acid, NaOH, tin(II), copper(II), chloramine‑T, colour reagents, AgNO3) and the liberation/absorption apparatus (air‑flow, absorber solutions).
- Quality controls: Defines the recovery factor for the liberation apparatus, blank tests, calibration procedures and precision data (Annex A).
- Safety and waste: Strong warning - hydrogen cyanide and salts are toxic. Work in a fume hood, use gloves, and manage cyanide waste as special toxic waste.
Practical applications and users
ISO 11262:2011 is used by:
- Environmental and commercial analytical laboratories conducting soil contamination assessments.
- Regulatory agencies and consultants performing site investigations and remediation verification.
- Mining, metallurgy and industrial operators monitoring legacy cyanide contamination from metal processing.
- Research laboratories studying cyanide speciation and soil chemistry.
Benefits include standardized, comparable total cyanide results for regulatory compliance, risk assessment and remediation decision‑making.
Related standards
Keywords: ISO 11262:2011, soil quality, total cyanide, cyanide determination, photometric method, titrimetric method, orthophosphoric acid, alkaline extraction, environmental laboratory.
