Determination of Sodium Lauryl Ether Sulfate

Significance of the Topic

Determining the content of sodium lauryl ether sulfate (SLES) is essential for quality control in detergent and personal care product manufacturing. Accurate quantification of this anionic surfactant ensures product performance, regulatory compliance and cost efficiency in industrial and laboratory settings.

Objectives and Study Overview

The primary aim of this application note is to present a precise thermometric titration method for quantifying SLES in commercial formulations. Key objectives include

• Establishing a robust titration protocol using cetyl pyridinium chloride (CPC) as titrant
• Defining optimal experimental parameters for reproducible endpoint detection
• Validating the approach with a model product (“Sulfotex 60/40”)
• Assessing and correcting for method blank to enhance accuracy

Methodology and Instrumentation

The procedure is based on exothermic reaction between anionic SLES and cationic CPC. A standardized 0.7 mol/L CPC solution is prepared in propan-2-ol and water. Samples containing approximately 60 % SLES are dissolved in water with acetone to disrupt micelles, then titrated to a single thermal endpoint. Key parameters include a titrant delivery rate of 2 mL/min, one exothermic endpoint, data smoothing factor of 60, stirring speed setting at 10, and a 15 s delay before titration begins. Method blank determination is performed for each product type to correct for background thermal signals.

Used Instrumentation

• Thermometric titrator with precise temperature sensing and automated endpoint detection
• Magnetic stirrer for sample dissolution and titration mixing
• Analytical balance for accurate sample weighing
• Volumetric flasks and glassware for solution preparation

Main Results and Discussion

Analysis of the model product “Sulfotex 60/40” yielded an average SLES content of 62.1 ± 0.12 % (n=6). A linear response was observed in blank determination with an intercept of 0.0928 mL CPC, R2=0.99995, demonstrating excellent method precision and accuracy. The inclusion of acetone effectively mitigated micelle interference on the titration curve, enabling a clear exothermic endpoint.

Benefits and Practical Applications

This thermometric titration approach offers

• High accuracy and reproducibility for routine quality control
• Rapid analysis with minimal sample preparation
• Reduced operator bias due to automated endpoint detection
• Flexibility to adapt to different surfactant formulations through blank correction

Future Trends and Potential Applications

Advances in sensor technology and data analytics are expected to further enhance thermometric titration. Potential developments include inline process monitoring, use of greener solvents for micelle disruption, and integration with laboratory information management systems to streamline QA/QC workflows.

Conclusion

The described thermometric titration method provides a reliable, efficient and accurate way to determine sodium lauryl ether sulfate in commercial products. Its automation and precision make it well suited for industrial and research laboratories focused on surfactant quality control.

Reference

• Thermo. Titr. Application Note No. H-039, Thermo Fisher Scientific