Overview
ISO 2870:2009 - "Surface active agents - Detergents - Determination of anionic-active matter hydrolysable and non-hydrolysable under acid conditions" - specifies a laboratory method to quantify anionic-active matter in detergents that is hydrolysable or non‑hydrolysable under acidic conditions. The scope covers common anionic surfactants such as alkyl sulfates, alkyl hydroxysulfates, and alkylphenol/fatty‑alcohol ethoxysulfates. Results are expressed in mmol/100 g (or converted to mass percent when molecular weight is known).
Key topics and technical requirements
- Principle: Two-part analysis - titration of an aliquot for total anionic-active matter, and acid hydrolysis (reflux) of a second aliquot followed by titration to determine non‑hydrolysable fraction. Hydrolysable content = total − non‑hydrolysable.
- Titration methods: Use either the two‑phase visual/manual or mechanical titration (ISO 2271) or the potentiometric two‑phase titration (EN 14480).
- Hydrolysis: Reflux an aliquot with sulfuric acid (solution c(H2SO4) = 490 g/L) for 3 hours. If oxidants are present, destroy them first with sodium sulfite (c(Na2SO3) = 20 g/L).
- Reagents and solutions: Key reagents specified include benzethonium chloride (Hyamine 1622) volumetric solution (0.004 mol/L) for titration, phenolphthalein indicator, NaOH solutions for neutralization, and analytical‑grade water (ISO 3696).
- Apparatus: Standard lab equipment plus a 250 mL conical flask, reflux condenser with ground glass joints.
- Calculations and expression: Results calculated in mmol/100 g using titrant volume and concentration; hydrolysable fraction derived by subtraction.
- Performance: Repeatability limit: difference between duplicate determinations by same analyst ≤ 2% of mean. Reproducibility limit between labs ≤ 4% of mean.
- Sampling and reporting: Sample preparation per ISO 607; test report must reference ISO 2870 and include sample ID, methods used, results and any deviations.
Applications and users
- Quality control and production labs at detergent and surfactant manufacturers to monitor product composition.
- Environmental and regulatory testing where distinction between hydrolysable and non‑hydrolysable anionic surfactants is required.
- R&D and formulation laboratories assessing stability and degradability of anionic surfactants.
- Third‑party testing and certification bodies performing compliance testing.
Related standards
- ISO 2271 - Two‑phase titration for total anionic-active matter (manual/mechanical)
- EN 14480 - Potentiometric titration in two phases
- ISO 3696 - Water for laboratory use
- ISO 607 - Sample preparation and division
Keywords: ISO 2870:2009, anionic-active matter, detergents, acid hydrolysis, potentiometric titration, two-phase titration, benzethonium chloride, alkyl sulfates, ethoxysulfates.
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