RP-HPLC studies of alcohol ethoxy propoxylates

In this study, we examined the chromatographic behaviour of non-ionic surfa ctants of the fatty alcohol polyethylene oxide polypropylene oxide type. We focused on the influence of the aliphatic chains, the degree of alkoxylati on and the position of the polyethylene oxide or the polypropylene oxide bl ocks relative to the fatty alcohol chain on the resultant chromatograms. Th e studies were carried out with octyl-modified or octaclecyl-modified silic a gel as the stationary phase and with various isocratical eluant mixtures consisting of methanol/water or acetonitrile/water. The retention behaviour of alkyl polyethylene oxide polypropylene oxide surfactants is mainly dete rmined by the aliphatic chains and for all alcohols and degrees of alkoxyla tion studied produces a peak with only slight splitting or no splitting at all. The chromatograms of the alkyl polypropylene oxide polyethylene oxide surfactants have peaks with strong structures that are caused by the indivi dual polypropylene oxide homologues. When plotting the homologue number aga inst the logarithm of the capacity factor, characteristic straight lines re sult for the individual surfactants. Their position depends on the constitu tion of the surfactants and the chromatographic conditions.