Commercial products of ethoxylated sulfonate surfactants are of current interest due to their tolerance towards hard water like sea-water. An analytical HPLC-method has been worked out which can detect and quantify the distribution of the various ethoxylated sulfonate isomers, R-(EO)x-SO3- (x = 2 - 15), at sea-water salinities. The different isomers of unconverted alcohols, R-(EO)x-OH, and other possible impurities, R-(EO)x-R, in the commercial product are also separated. The method has been worked out using a commercial product of the type C9-Ph-(EO)6-SO3Na and C8-Ph-(EO)3-SO3Na of two different suppliers. The chromatographic separation is based on a mixed-mode reversed-phase/ion-exchange column, and the analysis can be implemented as a quality-test of the commercial product.
