Surfactant Content by Two Different Potentiometric Titration Methods

This application note provides a complete solution to determine surfactant content. Parallel potentiometric titration is a streamlined method for monitoring the correct formulation in personal hygiene and cosmetic products.

What Are Anionic Surfactants?

Anionic surfactants are the primary components of personal hygiene and cosmetic products such as shower gels and shampoos. Anionic surfactant content must be monitored to achieve the correct formulations. Anionic surfactant content is generally determined using sophisticated analytical techniques such as separation methods (chromatography) or NIR spectroscopy. However, such techniques are rather time consuming, may require a long sample preparation and calibration of the instruments, and should be performed by well-trained and skilled operators.

How Can Anionic Surfactant Content Be Determined Quickly and Easily? 

Titration with surfactant-sensitive electrodes (SSEs) represents a valuable alternative to analytical techniques such as chromatography or spectroscopy. Titration is less expensive and easier to perform, and it does not require expert-level knowledge on the part of the operator. Using Titration Excellence T9, two different titration methods for the surfactant content determination of the same sample can be run in two beakers at the same time. Thus, the results from different techniques can be directly compared to ensure accuracy.

Method and Principle of Titration

The two methods are synchronized to simultaneously perform the analyses at Towers A and B on an InMotion™ Autosampler with two towers. This is achieved by creating a series sequence consisting of two sample series based on two different methods.
Precipitation reaction of anionic surfactant e.g. SDS (sodium dodecyl sulfate) with cationic surfactant Hyamine:

SDS- + Hyamine+ → SDS-Hyamine (↓)

Once the SDS-Hyamine complex is formed, it precipitates in the beaker. This leads to a slight increase of the turbidity of the solution, i.e. the solution becomes slightly milky indicative of reaction completion.