Quantitative analysis of ethoxylated alcohols by supercritical fluid chromatography

This work was undertaken to develop a relatively simple, rapid, reproducible and accurate method for measuring the ethylene oxide distribution, overall ethylene oxide ratio, and percent free alcohol in ethoxylated alcohols. Using single isomer ethoxylate standards comprised of from one to eight ethylene oxide units per alcohol, a response factor correlation for the flame ionization detector on a supercritical fluid Chromatograph was established. Response factors for ethoxylates with higher than eight ethylene oxide units were estimated by extrapolation of this correlation. Supercritical fluid Chromatographic separation of ethoxylates was accomplished using a density-programmed carbon dioxide mobile phase and a poly (dimethylsiloxane) coated open tubular column. The validity and accuracy of this method was demonstrated by comparing its results for unreacted alcohol levels, ethylene oxide-to-alcohol average ratios, and weights of samples injected relative to internal standards with values measured independently by standard methods. In addition, supercritical fluid Chromatographic determinations of ethylene oxide molar distributions are in agreement with theoretical Weibull-Nycander distributions. Presented in part at the AOCS Annual Meeting in PHoenix, AZ, in May 1988.