Overview
ISO 6703-1:1984 - "Water quality - Determination of cyanide - Part 1: Determination of total cyanide" specifies validated laboratory procedures for measuring total cyanide in water. The standard defines total cyanide as simple and complex bound cyanides that are converted to hydrogen cyanide (HCN) under the method conditions. It describes the liberation and absorption of HCN and three alternative quantitative determination techniques suitable for routine environmental and effluent testing.
Key Topics
- Scope and definition
- Measurement of total cyanide in water (method applicable up to 100 mg/L by dilution).
- Excludes mononitriles, cyanate, thiocyanate and cyanogen chloride from “total cyanide” as defined.
- Sample handling & stabilization
- Immediate addition of stabilizers (e.g., NaOH, phenolphthalein, Sn(II) chloride) to each litre of sample to prevent loss and alteration.
- Homogenization guidance for samples containing undissolved cyanides.
- Liberation and absorption (common preparative step)
- Acid digestion in presence of copper(I) and stripping of liberated HCN with an air carrier into NaOH absorption solution.
- Equipment: three‑necked distillation flask, condenser, absorption vessels, flowmeter and wash bottle.
- Analytical methods (three alternatives)
- Photometric method with pyridine/barbituric acid (sensitive range 0.002–0.025 mg CN) - forms a red‑violet dye after chloramine‑T oxidation.
- Titrimetric method using the Tyndall effect (applicable >0.005 mg CN).
- Titrimetric method using a chemical indicator (applicable >0.05 mg CN).
- Interferences and limitations
- Table of interfering ions and limiting concentrations (e.g., sulfide, thiosulfate, nitrite, iron, silver, mercury, pyridine) with recommended sample dilution or alternative method if exceeded.
- Safety
- Strong warnings on cyanide toxicity, need for fume hood, protective equipment and detoxification of wastes. Other reagents (e.g., pyridine, chloramine‑T) are hazardous.
Applications
ISO 6703-1 is used by:
- Environmental and public‑health laboratories for water quality monitoring.
- Industrial and municipal wastewater labs for effluent control and compliance.
- Laboratories servicing mining, electroplating and chemical industries where cyanide is used or discharged.
- Regulatory agencies and consultants validating cyanide concentrations for permits and risk assessments.
Keywords: ISO 6703-1, total cyanide, cyanide determination, water quality, photometric pyridine barbituric, Tyndall titration, cyanide analysis, sample preparation, interferences.
Related Standards (if applicable)
- ISO 6703-2: Determination of easily liberatable cyanide.
- ISO 6703-3: Determination of cyanogen chloride.
- ISO 6703-4: Determination of cyanide by diffusion (pH 6) - draft stage at time of part 1.
