ISO 11262:2011

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

• ISO 17380 (automated ELC and total cyanide methods) - referenced in the introduction.
• Normative references cited: ISO 3696, ISO 9297, ISO 11464, ISO 11465, ISO 14507 - relevant for water quality, titration, and soil sample pretreatment.

Keywords: ISO 11262:2011, soil quality, total cyanide, cyanide determination, photometric method, titrimetric method, orthophosphoric acid, alkaline extraction, environmental laboratory.