Analysis of polyethoxylated surfactants in microemulsion-oil-water systems

A normal-phase method for the separation of ethylene oxide number (EON) oli gomers by high performance liquid chromatography (HPLC) is described. Isocr atic HPLC with mixed solvent on silica column allows to separate oligomers up to EON = 18. Gradient programming moves the limit up to EON = 20. For hi gher EON values (up to 50) a NH2 column has to be used, either with isocrat ic or gradient mode. Detection was performed using UV detector. The partiti on of surfactant in the oil-water system over the entire concentration rang e below the CMC was determined. Surfactant-oil-water systems were studied a ccording to the unidimensional scan. The surfactant content in the oil, mic roemulsion and water phases was determined by HPLC. The addition of a lipop hilic alcohol in a Winsor III system produced a decrease in the partition c oefficient of the surfactant between the water and oil phases. (C) 2000 Els evier Science B.V. All rights reserved.