A high-performance size-exclusion chromatographic column packed with Asahipak GS-3 10 vinyl alcohol copolymer gel was investigated for its applicability to the analysis of non-ionic surfactants with mobile phases containing water and acetonitrile or other organic solvents in various ratios. The surfactant series consisted of R(OCH2CH2),0H, where R is an alkylaryl group and n = l-100.
In the water-rich region, with acetonitrile concentrations of O--30%, surfactants either were not eluted or their elution was extremely delayed, indicating a hydrophobic interaction between the gel and the alkylaryl group in the surfactant. In the acetonitrile-rich region, with acetonitrile concentrations of 60-loo%, the surfactants were eluted relatively rapidly in order of decreasing molecular weight, without a fine separation between compounds with different n values. These results indicate that the organic solvent effectively inhibited the hydrophobic interaction and that size exclusion was the predominant separation mechanism. In the intermediate region, with 30-60% acetonitrile concentrations, the surfactants were eluted in the same order as for the acetonitrile-rich region, but less rapidly and with a fine separation between n values. The results indicate that the separation mechanism is mainly hydrophobic interaction between the alkylaryl groups and the gel, the hydrophobicity of the gel being too weak for effective interaction with the oxyethylene groups.
The results indicate that the Asahipak GS-3 10 hydrophilic polymer gel column can be effectively employed for the practical, efficient high-performance liquid chromatographic analysis of non-ionic surfactants.