Overview
ISO 2268:1972 is an international standard established by the International Organization for Standardization (ISO) that specifies a reliable analytical method for determining polyethylene glycols (PEGs) and non-ionic active matter (adducts) in surface active agents (non-ionic). Known as the Weibull method, it leverages the distinct solubility characteristics of polyethylene glycols and non-ionic adducts in sodium chloride solution and organic solvents such as ethyl acetate, chloroform, and acetone to achieve separation and quantification.
This standard is crucial for quality control and formulation accuracy in the production of non-ionic surfactants, widely used in detergents, cosmetics, and industrial applications. The method is applicable to commercial non-ionic surfactants containing 2 to 80 oxyethylene groups per molecule.
Key Topics
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Scope of Applicability
ISO 2268:1972 applies to alkyl polyethoxylates and alkylphenol polyethoxylates, which are non-ionic surfactants often manufactured with polyethylene glycol as a by-product. It covers both liquid and solid samples.
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Principle of the Weibull Method
- Polyethylene glycols and non-ionic condensates are both soluble in sodium chloride solution.
- Non-ionic condensates dissolve in ethyl acetate; PEGs do not.
- Separation is conducted by dissolving the sample in ethyl acetate, extracting PEGs with sodium chloride solution, then isolating PEGs by extraction with chloroform, and evaporating solvents for weighing residues.
- The ethyl acetate fraction, containing the non-ionic active matter (condensates), is evaporated and weighed separately.
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Reagents and Equipment
- Use of high-purity reagents such as ethyl acetate, sodium chloride solution, chloroform, anhydrous acetone, and petroleum ether.
- Common laboratory glassware including separating funnels (ampoules à décanter), conical flasks, and filtration equipment.
- Temperature control is critical: all separation and extraction steps are performed at controlled temperatures around 35 ± 1°C to ensure accurate solubility separation.
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Procedure Highlights
- Sample preparation involves heating and agitation to obtain a clear solution or melt for solids.
- Sequential extraction steps with sodium chloride solution and ethyl acetate to separate PEGs and condensates.
- Chloroform extraction for PEG isolation followed by solvent evaporation and residue weighing.
- Repeated washing steps improve purity and accuracy.
- Calculation of PEG and active matter content is based on mass percentages relative to the sample size.
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Result Documentation
The test report must document sample identification, method references, test results, test conditions, any procedural deviations, and observations impacting results.
Applications
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Quality Control in Surfactant Production
Ensures correct quantification of polyethylene glycols and active non-ionic components, which affects performance and consistency of detergents, emulsifiers, personal care products, and industrial surfactants.
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Research and Development
Provides a standardized approach to analyze by-products and purity of novel surfactant formulations.
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Regulatory and Compliance Testing
Facilitates adherence to material specifications in international trade and manufacturing standards by providing a reproducible analytical method.
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Material Characterization
Assists in characterizing the composition of polyethoxylated alcohols and alkylphenol derivatives utilized in various chemical processes.
Related Standards
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ISO 2878: Surface Active Agents - Alkylphenol Ethoxylates - Determination of non-ionic surfactant content
Focuses on broader non-ionic surfactant content analysis methods complementary to ISO 2268.
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ISO 22715: Cosmetics - Packaging and Labelling
Relevant for end-use of non-ionic surfactants in cosmetic products following compliant formulation.
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ISO 9001: Quality Management Systems
Supports the quality assurance framework within organizations using ISO 2268 analytical methods.
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ASTM D2167: Polyethylene Glycol Content in Nonionic Surfactants
Offers alternative or comparative methods for analyzing PEG content in surfactant solutions.
Keywords: ISO 2268, non-ionic surfactants, polyethylene glycols determination, surface active agents analysis, Weibull method, ethyl acetate extraction, sodium chloride solution, PEG quantification, surfactant quality control, analytical standard for surfactants.