Analysis of Surfactants in toothpastes by HPLC

Importance of the Topic

Surfactants are key functional ingredients in toothpaste formulations, responsible for foaming, cleaning efficiency and sensory properties. Accurate quantification of these compounds ensures product consistency, consumer safety and regulatory compliance in oral care products.

Objectives and Study Overview

This work evaluates a reversed-phase HPLC method (VEV0029J) for the separation and quantification of sodium soaps (C8–C18) and α-sulpho fatty acid methyl esters (C10–C18) in toothpaste matrices. The goal is to establish a reliable analytical approach for routine quality control and formulation development.

Methodology

The analysis employs an Eurospher 100-5 C18 column (250 × 4.0 mm ID) under isocratic conditions. Mobile phase consists of methanol/water (90:10) with 0.25 M sodium perchlorate. Key parameters:

• Flow rate: 1.5 mL/min
• Column temperature: 25 °C
• Injection volume: 20 µL
• Detection: Refractive index (RI)

Instrumentation Used

• Reversed-phase HPLC system equipped with Eurospher C18 column
• Refractive index detector for non-UV-absorbing surfactants

Main Results and Discussion

The method achieved baseline separation of sodium soaps (chain lengths C8 to C18) and α-sulpho methyl esters (C10 to C18). Retention times increased systematically with alkyl chain length. Refractive index detection provided stable and reproducible peak responses. The isocratic elution simplified the protocol while maintaining resolution across all analytes.

Benefits and Practical Applications

• Rapid and reproducible quantification of key surfactant classes in toothpaste
• Suitable for routine quality control labs in oral care product manufacturing
• Supports regulatory compliance by ensuring accurate composition data

Future Trends and Opportunities

Potential enhancements include coupling with evaporative light scattering or charged aerosol detection to boost sensitivity, adopting gradient elution for even faster throughput, and integrating mass spectrometry for structural confirmation of novel surfactant variants.

Conclusion

The isocratic RP-HPLC method described offers a robust, reproducible and user-friendly approach for analyzing surfactants in toothpaste formulations. It meets the demands of quality assurance and formulation development in the oral care industry.