Mapping of Polyethers Using Two-Dimensional Liquid Chromatography With Coupled Density and RI Detection

Abstract

Two-dimensional liquid chromatography is a useful method for the characterization of nonionic surfactants, such as ethoxylated fatty alcohols with respect to the distributions of molecular weight, chemical composition, and functionality. In the first dimension, liquid chromatography under critical conditions is used to separate according to functionality. The fractions thus obtained, which consist of pure homologous series, are analyzed by size exclusion chromatography. From these data, a three-dimensional map is established. With a combination of a density detector and a refractive index detector in both dimensions, the correct altitudes in such a map are obtained. By this technique, the contribution of preferential solvation in each peak can also be determined.