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ISO 2271

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ISO 2271

ISO 2271, published by the International Organisation for Standardisation (ISO), ‘Surfactants – Detergents — Determination of the anionically active substance by manual or mechanical direct two-phase titration’, i.e. ‘Surfactants – Detergents – Determination of the anionic active substance by manual or mechanical direct two-phase titration’. The current text is ISO 2271:1989; any revisions and the status of national implementation should be checked against the relevant official sources before work commences.

Note on regulatory status: ISO 2271 is an analytical chemistry method; it is not a biological or toxicological test. It is frequently used to determine the content of anionic surfactants in products containing detergents and surfactants, as well as for verifying product specifications and for quality control. Sister standards based on a similar principle include ISO 2871-1 and ISO 2871-2 (determination of cationic surfactants), as well as other two-phase titration methods that have been adapted for various matrices.

Basic principle

The method is based on the titration of anionic surfactants with a standardised cationic surfactant solution (usually Hyamine 1622, i.e. benzethonium chloride or cetylpyridinium bromide) in a chloroform/water two-phase system. Anionic and cationic surfactants migrate into the chloroform phase by forming ion pairs at the water–oil interface. During the titration:

  • Initially, the anionic surfactant is present in excess, and the chloroform phase turns pink when a mixed indicator (dimidium bromide + disulfin blue) is used.
  • During the titration, the cationic surfactant neutralises the anionic surfactant; at the equivalence point, the colour of the chloroform phase changes to blue or grey-blue.
  • The colour change is taken as the endpoint of the titration.

What is it for?

The ISO 2271 standard is used for the following scientific, technical and regulatory purposes:

  • Verification of product specifications: determining whether products containing detergents or surfactants comply with the specified content of anionic active ingredients
  • Quality control: Monitoring consistency between production batches and ensuring product quality
  • Formulation development: Optimisation of new detergent formulations and evaluation of the balance of active ingredients
  • Raw material control: Verification of the active ingredient content of raw materials for surfactants
  • Competitive/comparative analysis: Comparison with reference products or equivalent products
  • Support with the preparation of authorisation documentation: provision of data for the summary and technical dossier of laundry and cosmetic products (in accordance with the applicable legislation)
  • Verification of labelling and information: verification of the active ingredient concentrations stated on the product label
  • Data for environmental assessment: Provision of baseline data for assessing the fate and degradation processes of surfactants in the environment
  • Evidence-based approach: a contribution to the holistic assessment of the product in conjunction with other analytical and physico-chemical data

ISO 2271 specifies the total amount of anionic surfactants; no distinction is made between specific types of anionic surfactants. The results should be interpreted in the context of the complete product formulation, other analytical data and the specification requirements.

At NanoTest, we carry out the determination of anionic surfactants in accordance with ISO 2271, applying scientific rigour within the framework of our accredited laboratory infrastructure and our quality management system.

For your testing of anionic active substances in accordance with ISO 2271, you can contact NanoTest to obtain information on the suitability of the method, sample preparation, titration strategy (manual or mechanical), the assessment of interfering factors, the test schedule and the reporting procedures.

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