Influence of the HLB parameter of nonionic surfactants on normal and reversed-phase thin layer chromatography

Normal and reverse Thin Layer Chromatography was performed in order to study the relationship between the hydrophilic-lipophilic balance of nonionic surfactants and its chromatographic migration. Experiments in both normal (silica-gel) and reverse (octadecyl silane modified) Thin Layer Chromatography plates (TLC) were carried out using the same solvent compositions. The influence of solvent composition in a mixed system has also been studied in order to determine the mechanism of the chromatographic separation of nonionic surfactants. It was observed that the chromatographic separation followed the model of differential partition of surfactants between liquid pseudophases. Chromatographic retention was found to be highly dependent on the number of ethylene oxide units in the surfactant molecules. In reverse TLC it was also dependent on the alkyl chain length. The relative capacity factor (normal respect to reverse) was also found to be highly dependent on the number of ethylene oxide units. (C) 2001 Elsevier Science B.V. All rights reserved.