Determination of Surfactant Content by Conductometric and Potentiometric Titration

This application note provides a complete solution to determine the surfactant content for monitoring the correct formulation in shower gels and shampoos by conductometric and potentiometric titration.

How to Attain Correct Formulations in Shower Gels and Shampoos?

Anionic surfactants are primary components of personal hygiene and cosmetic products such as shower gels and shampoos. Anionic surfactant content must be monitored to achieve 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.

Is There an Alternative to More Easily Determine Anionic Surfactant Content?

Titration with electrochemical probes such as surfactant sensitive electrodes or conductometric sensors represents a valuable alternative to sophisticated chromatography and spectroscopy techniques since titration is less expensive, easier to perform and generally does not require a high degree of operator knowledge and training.

Method and Principle of Titration

Using a Titration Excellence T9, two methods for surfactant content determination using conductometric and potentiometric titration can be run in two beakers at the same time. The results from these different titration techniques can be directly compared. The two methods are synchronized to perform the analyses at Towers A and B on an InMotion™ Autosampler simultaneously. For this method, Tower A performs the conductometric titration whereas Tower B performs the potentiometric titration. 

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.