Surfactants are amphiphilic molecules having both an hydrophilic and lipophilic interaction with molecules of a given system. Those interactions have been characterized by the use of HLB (Hydrophilic-Lipophilic Balance) since the mid-50s’. Different calculation technics have been promoted. One of the more popular methods is the Griffin’s method which is based on the ratio of the hydrophilic portion of the molecular mass to the complete molecular mass and is expressed on a scale is between 0 and 20. Although this method gives accurate results for the characterization of pure molecules, it is less convenient in its use when working with mixtures of molecules which are abundant in the current chemical industry. Moreover, new biosurfactants that are manufactured thanks to biotechnology also lead to mixtures that are difficult to analyze due to the complex determination of the molecular weights.  An empirical method has been developed by the University UCCS of Lille in order to measure the hydrophilic-lipophilic character of surfactants. This method is named SLOPE PIT (Phase Inversion Temperature) and is based on the principle of conductivity measurements of an emulsion before and after the phase inversion temperature. It has been first implemented using pure surfactants which enabled us to correlate the SLOPE PIT values to those predicted <i>via</i> HLB calculations. However, we didn’t know if this technique is applicable for surfactant mixtures.  The study evaluate the hydrophilic-lipophilic character of surfactants from Oleon’s Crop Protection portfolio, which contains mostly mixtures, using the SLOPE PIT measurement. From a statistical point of view, we studied the correlation between surface properties and SLOPE PIT measurements with the goal of setting up a new scale using only SLOPE PIT.

SLOPE PIT method to characterize surfactants

256th National Meeting (2018)

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