ISO 10530:1992

Overview

ISO 10530:1992 specifies a photometric method using methylene blue for the determination of dissolved sulfide in water. The standard covers filtration and preservation, stripping of sulfide into a zinc acetate absorber, formation of leukomethylene blue and oxidation to methylene blue, and photometric measurement at 665 nm. The method is applicable to natural and waste waters requiring filtration and is designed for a mass concentration range of 0.04 mg/L to 1.5 mg/L (higher concentrations by dilution).

Keywords: ISO 10530, dissolved sulfide, methylene blue method, water quality, photometric method, 665 nm.

Key topics and requirements

• Scope and range
  • Target range: 0.04–1.5 mg/L sulfide as S (extendable by dilution).
  • Not suitable for waters that cannot be filtered as specified.
• Analytical principle
  • Filtration → conserve sulfide with ascorbate (pH 10) → strip with nitrogen → absorb into zinc acetate → react with N,N-dimethyl-p-phenylendiamine (colour-forming reagent) + ammonium iron(III) sulfate → measure absorbance at 665 nm.
• Interferences (non-significant up to stated concentrations)
  • Cyanide ≤ 2 mg/L, Iodide ≤ 20 mg/L, Thiosulfate ≤ 900 mg/L, Thiocyanate ≤ 900 mg/L, Sulfite ≤ 700 mg/L.
  • Carbon disulfide < 10 mg/L and ethyl mercaptan < 1 mg/L do not interfere.
• Sampling and preservation
  • Filter at sampling (three-ring piston syringe or membrane device, 0.45 µm), add ascorbate preservative, limit filtration time to ~5 min and analyze preserved filtrate within 24 hours.
• Calibration and quality control
  • Use a calibration curve (linear segment) with sodium sulfide standards; Annex A describes iodometric standardization of stock solution.
• Apparatus & reagents
  • Spectrometer or filter photometer for 665 nm, 1 cm cuvettes, high-purity N2 gas (≈40 L/h), specified reagent solutions (zinc acetate, phthalate buffer pH 4.0, etc.).

Practical applications

• Monitoring water quality in rivers, lakes and industrial effluents for toxic sulfide levels.
• Compliance testing for wastewater treatment plants and environmental discharge permits.
• Routine laboratory determination of dissolved sulfide in environmental and regulatory laboratories.
• Assessing corrosion risk or odor problems related to sulfide in water systems.

Who should use this standard

• Environmental and municipal water quality laboratories
• Wastewater treatment operators and process engineers
• Regulatory agencies and compliance auditors
• Environmental consultants conducting field sampling and lab analysis

Related standards

• ISO 5667-3:1985 - Guidance on preservation and handling of water samples (referenced for sampling and preservation).
• Annex A (ISO 10530) - normative procedure for standardizing sulfide stock solutions by iodometry.

This concise summary highlights the practical workflow and technical limits of ISO 10530:1992 for dissolved sulfide analysis using the methylene blue photometric method.