SEPARATION OF OLIGOMERS OF NONYLPHENYLETHYLENE OXIDE ON A POROUS GRAPHITIZED CARBON COLUMN

The retention of nonylphenyl ethylene oxide oligomer surfactants was d etermined on a porous graphitized carbon (PGC) column using water-meth anol mixtures as eluents. Linear correlations were calculated between the logarithm of the capacity factor (k') and the methanol concentrati on in the eluent. To test the validity of the hypothesis that in the c ase of homologous series of solutes the intercept and slope values are intercorrelated linear correlation was calculated between the two chr omatographic parameters. To elucidate the role of the length of the po lar ethylene oxide chain in the retention linear correlations were cal culated between the chromatographic parameters and the number of ethyl ene oxide groups per molecule. Nonylphenyl ethylene oxide oligomers we re well separated on the PGC column. Significant linear relationships were found between the corresponding chromatographic parameters indica ting that the solutes behave as a homologous series of compounds. The retention of surfactants increased linearly with increasing number of ethylene oxide groups per molecule indicating hydrophilic interactions between the solutes and the surface of PGC support. (C) 1997 Elsevier Science B.V.