Determination of Polarity Terms of Some Nitrogen-Containing Surfactants and Simulated Hydrophobic Tail Models by Gas Chromatography

Some polarity terms of two groups of nitrogen-containing surfactants (six alkanolamides and nine polyoxyethylenated long chain amines) are measured through gas chromatography. The apparent methanol carbon number (C_(MeOH)) and polarity index (IP) values are determined on the investigated surfactants as stationary phases in packed columns. Similarly, C_(MeOH) and IP values are determined on simulated hydrophobic tail (SHT) models. The obtained results reveal that the introduction of SHT approach permits the distinction between the polarities of different surfactants and their head groups. The measured polarity terms are discussed as related to hydrophile-lipophile balance (HLB) number and the hydrophobic group carbon number (RCN). Some equations relating the measured polarity values and these variable have been developed.