Commercial ethoxylated tributylphenol oligomers were separated according to the number of ethylene oxide (EO) units by reverse phase high performance liquid chromatography on porous graphitic carbon column at different eluent concentration (methanol-water). The retention time increased with decreasing methanol concentration of the eluent and increased with the ethylene oxide unit number. Linear correlation was found between Igk0' and fraction of EO number. Stepwise regression analysis indicated the appearance of the helical form of the oligomers.