SEPARATION AND IDENTIFICATION OF NONYLPHENYLETHYLENE OXIDE OLIGOMERS BY HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHY WITH UV AND MASS-SPECTROMETRIC DETECTION

Nonylphenylethylene oxide surfactants were separated on an alumina col umn using an ethylene oxide-n-hexane mixture as the mobile phase, and UV and MS detection. Several well separated, large peaks and some smal l, partly separated peaks were detected. It was found that the main fr actions elute log-equidistantly and they correspond to the nonylphenyl ethylene oxide oligomers with a given number of ethylene oxide units, and the small peaks contain isomers, probably surfactants with differe nt positions of the nonylgroup at the phenyl ring. The method validati on showed no significant differences between the intra-day and inter-d ay values of the area percentages and their standard deviations, showi ng the good reproducibility of the determination of the area percentag es during at least three consecutive days. Significant differences wer e found between the intra-day and inter-day values of the standard dev iation of the retention times, which indicates that the determination of the retention time is less reproducible than that of the area perce ntages. (C) 1998 Elsevier Science B.V. All rights reserved.