Overview
EN ISO 2870:2009 (ISO 2870:2009) specifies an analytical method for the determination, in detergents, of anionic-active matter hydrolysable and non‑hydrolysable under acid conditions. The scope covers common anionic surfactants such as alkyl sulfates, hydroxysulfates, alkylphenol ethoxysulfates and fatty alcohol ethoxysulfates. Results are reported as amount of anionic‑active matter (mmol/100 g) or, when molecular weight is known, as mass percent.
Key topics and technical requirements
- Analytical principle: two‑phase titration of a test solution with benzethonium chloride (Hyamine 1622), using either the manual/mechanical direct two‑phase titration (ISO 2271) or the potentiometric two‑phase titration (EN 14480).
- Acid hydrolysis: a separate aliquot of the sample is refluxed with sulfuric acid for 3 h to hydrolyze acid‑labile anionic species; oxidizing agents (if present) must be destroyed with sodium sulfite before hydrolysis.
- Neutralization and titration: after reflux, the solution is neutralized (phenolphthalein indicator, NaOH) and the non‑hydrolyzed anionic fraction is titrated as above.
- Calculations: total, non‑hydrolyzable and hydrolyzable contents are calculated in mmol/100 g using titrant volume and concentration. Conversion to mass percent requires knowledge of the mean relative molecular mass of the surfactant fraction.
- Precision: repeatability limit ≈ 2% of the mean; reproducibility limit ≈ 4% of the average (laboratory intercomparison).
- Key reagents & apparatus: sulfuric acid, sodium sulfite, phenolphthalein, NaOH solutions, benzethonium chloride standard solution (~0.004 mol/L), conical flask with reflux condenser; use high‑purity water per ISO 3696 and follow sample division per ISO 607.
Applications and users
- Quality control in detergent manufacturing to quantify acid‑labile vs. stable anionic surfactants.
- Product formulation and R&D for verifying surfactant composition and behavior under acidic conditions.
- Regulatory and conformity testing where specification of anionic surfactant content is required.
- Environmental and waste water testing labs assessing surfactant forms that may hydrolyze in treatment processes.
- Typical users: analytical chemists, QC laboratories, standards bodies, and contract testing laboratories in the surface‑active agents and detergent industry.
Related standards
- ISO 2271 - Direct two‑phase titration for anionic-active matter
- EN 14480 - Potentiometric two‑phase titration method
- ISO 607 - Sample division for surfactants and detergents
- ISO 3696 - Water for analytical laboratory use
EN ISO 2870:2009 provides a standardized, repeatable procedure for separating and quantifying acid‑hydrolysable and non‑hydrolysable anionic surfactant fractions - essential for reliable detergent analysis and compliance testing.
