Overview
ISO 6121:1988 is an international standard established by the International Organization for Standardization (ISO) that specifies a precise analytical method for determining the content of alkane monosulfonates in technical alkane sulfonates. This method employs a direct two-phase titration technique involving an aqueous phase and a chloroform phase, enhanced by the presence of sodium sulfate. The titration is performed against a standardized volumetric cationic-active solution - benzethonium chloride - using a specialized mixed indicator comprising a cationic dye (dimidium bromide) and an anionic dye (acid blue 1).
This standard is essential for quality control and chemical analysis in industries where alkane sulfonates are used, ensuring the accurate quantification of alkane monosulfonates amid other components such as disulfonates that may interfere with measurements.
Key Topics
-
Scope and Applicability
The method applies to technical alkane sulfonates derived from sulfochlorination and sulfoxidation of paraffins with carbon chains ranging from 12 to 20 atoms. It focuses on the quantification of alkane monosulfonates in sodium salt form, critical for verifying product composition in surfactant manufacturing.
-
Two-Phase Titration Principle
The method uses an extraction system consisting of an aqueous phase mixed with sodium sulfate and an organic chloroform phase. The alkane monosulfonates react with a cationic-active titrant (benzethonium chloride). The endpoint is detected visually using the mixed dye indicator, which changes color when neutralization is complete.
-
Reagents and Materials
The standard specifies analytical-grade reagents, including:
- Chloroform (density ~1.48 g/ml) for the organic phase
- Anhydrous sodium sulfate solution (200 g/l)
- Benzethonium chloride standardized solution (~0.004 mol/l) as the titrant
- Mixed indicator comprising bromide of dimidium and acid blue 1 dyes
-
Test Procedure and Apparatus
The test involves carefully preparing a solution of the sample, mixing it with the reagents, and titrating it with the standard solution until the color change indicates the endpoint. Laboratory equipment such as burettes, volumetric flasks, pipettes (conforming to ISO standards), and stoppered graduated containers are required.
-
Calculation and Result Expression
The alkane monosulfonates content is calculated based on the volume of titrant consumed, its concentration, and the relative molecular mass of the monosulfonate. Results are reported as a mass percentage in the sample.
-
Precision and Reproducibility
The procedure delivers reliable results with a repeatability standard deviation of approximately 0.55% and a reproducibility standard deviation of around 1.57%, confirming its suitability for routine quality assurance.
Applications
-
Surfactant Quality Control
ISO 6121:1988 enables manufacturers of alkane sulfonate surfactants to accurately quantify the monosulfonate component. This ensures product uniformity in detergents and cleaning agents.
-
Industrial Chemical Analysis
The method supports detailed compositional analysis of alkane sulfonates used in various applications including emulsifiers, wetting agents, and industrial cleaners.
-
Regulatory Compliance and Product Specification
Adhering to this ISO standard helps companies comply with international regulations and market requirements for chemical purity and performance characteristics.
-
Research and Development
Laboratories that develop new surfactant formulations use this standardized titration method to assess the influence of mono- and disulfonates on product properties.
Related Standards
- ISO 607 – Sampling procedure for surface active agents and detergents
- ISO 648 – Glass laboratory pipettes specifications
- ISO 1042 – Volumetric flasks specifications
- ISO 385-1 – General specifications for burettes used in volumetric analysis
- ISO 2271 – Determination of active anionic matter by direct two-phase titration
- ISO 6845 – Determination of relative molecular mass of alkane monosulfonates
Keywords
Surface active agents, technical alkane sulfonates, alkane monosulfonates, two-phase titration, benzethonium chloride titration, chemical analysis, surfactant quality control, sodium sulfate extraction, analytical chemistry, ISO standards.
By following ISO 6121:1988, laboratories and manufacturers can ensure precise and repeatable measurement of alkane monosulfonates content, supporting product quality, regulatory adherence, and effective application of alkane sulfonate-based surface active agents.
Open preview (PDF)Surface active agents — Technical alkane sulfonates — Determination of alkane monosulfonates content by direct two-phase titration