Overview
ISO 2868:1973 specifies an analytical method for determining trace amounts of anionic-active matter stable to acid hydrolysis in detergents and surfactant formulations. The procedure targets non‑hydrolyzable anionic surfactants present alongside a large excess of hydrolyzable anionic matter. Samples are refluxed under acid conditions to hydrolyze labile components; the remaining stable anionic-active matter is quantified by a direct two‑phase titration (as described in ISO 2271). ISO 2868 is applicable to cyclic sulphonates in alkylphenol ether sulphates and small amounts of sulphonates in sulphated fatty alcohols.
Key topics and technical requirements
- Scope: Trace determination of acid‑stable anionic-active matter in detergent matrices where hydrolyzable anionic species are present in excess.
- Principle: Acid reflux hydrolysis to remove hydrolyzable surfactants, followed by extraction and two‑phase titration of the non‑hydrolyzable fraction.
- Essential reagents (as specified): chloroform, sulfuric acid (various normalities), sodium hydroxide solutions, benzethonium chloride titrant, phenolphthalein and mixed indicators, sodium lauryl sulphate standard.
- Apparatus: standard laboratory glassware including a 250 ml conical flask with ground‑glass joint and a water‑cooled reflux condenser.
- Procedure highlights:
- Weigh test portion containing 0.5–2 g of anionic-active matter.
- Reflux with sulfuric acid for 3 hours to hydrolyze labile species.
- Neutralize, remove inorganic salts (ethanol precipitation and filtration), extract with chloroform and indicator, then titrate using benzethonium chloride per ISO 2271.
- Expression of results: Calculated from titration volume, titrant normality, sample mass; if reporting as mass percent, the molar mass of the anionic matter must be known or previously determined.
- Precision: Within‑lab repeatability ~±1.5% of mean; between‑lab reproducibility ~±3% of mean.
Applications and users
ISO 2868 is practical for:
- Quality control laboratories in detergent and surfactant manufacturing
- Analytical chemists performing trace analysis of sulphonates and related anionic surfactants
- R&D teams formulating or reformulating surfactant blends where small amounts of stable anionic species must be quantified
- Regulatory and compliance testing where accurate quantification of non‑hydrolyzable anionic matter is required
Keywords: ISO 2868, detergents, anionic-active matter, acid hydrolysis, two-phase titration, cyclic sulphonates, alkylphenol ether sulphates, sulphated fatty alcohols, surfactant analysis, trace determination.
Related standards
- ISO 2271 - Surface active agents - Detergents - Determination of anionic‑active matter (direct two‑phase titration procedure).
Open preview (PDF)Surface active agents — Detergents — Anionic-active matter stable to acid hydrolysis — Determination of trace amounts
