Overview
EN ISO 16265:2012 (ISO 16265:2009 adopted by CEN) defines a laboratory method for measuring the methylene blue active substances (MBAS) index in water using continuous flow analysis (CFA). The standard covers MBAS determination in a variety of waters (groundwater, drinking water, surface water, wastewater, leachates) in the ranges 0.05–0.5 mg/L and 0.5–5.0 mg/L (results expressed as sodium dodecyl sulfate, SDS, equivalents). MBAS is a method‑defined indicator commonly used to estimate anionic surfactant content.
Key topics and technical requirements
- Principle: Sample mixed in a continuous flow with alkaline methylene blue to form ion‑pairs with MBAS; ion‑pairs extracted to trichloromethane (CHCl3), acidified and measured photometrically at 650 nm ± 10 nm. Results reported as SDS concentration.
- Analytical scope: Intended ranges 0.05–0.5 mg/L and 0.5–5.0 mg/L; other one‑decade ranges may be used case‑by‑case.
- Reagents & apparatus: Standard requires specific reagents (e.g., methylene blue, alkaline/acidified reagent solutions, trichloromethane) and CFA equipment; use reagent‑grade water and follow recommended degassing and preparation steps.
- Sampling and pretreatment: Filtration recommended for particles >100 µm; samples >5 mg/L MBAS must be diluted. Blank compensations are used to correct sample colour.
- Interferences: Cationic compounds, high humic acid (>20 mg/L), non‑MBAS surfactants at high concentration (>50 mg/L), strong reducing agents (e.g., sulfide/thiosulfate/hypochlorite), and high inorganic anions can bias results. Some interferences require removal (e.g., oxidation) before analysis.
- Performance & safety: CFA supports high throughput (many samples, up to ~100/h). The standard includes precision data and warns on hazardous wastes (trichloromethane, methanol) and the need for trained personnel.
Applications
- Routine monitoring of anionic surfactants in drinking water, surface water and wastewater
- Environmental compliance and process control at wastewater treatment plants and industrial effluents
- Screening of leachates and groundwater for surfactant contamination
- High‑throughput laboratory workflows using continuous flow analysis (CFA)
Who uses this standard
- Environmental and public‑health water testing laboratories
- Wastewater treatment operators and industrial environmental teams
- Regulatory authorities and compliance laboratories
- Contract testing labs and research institutions studying surfactant pollution
Related standards
- Normative references in EN ISO 16265: ISO 648, ISO 1042, ISO 3696 (laboratory glassware and water quality for analytical use).
- MBAS is a method‑defined parameter; users should consider complementary surfactant-specific methods when detailed compound identification is required.
Keywords: EN ISO 16265:2012, MBAS, methylene blue active substances, continuous flow analysis, CFA, water quality, anionic surfactants, sodium dodecyl sulfate, SDS, environmental monitoring.