Separation of broadly distributed nonylphenol ethoxylates and determination of ethylene oxide oligomers in textile lubricants and emulsions by high-performance liquid chromatography

A simple and rapid high-performance liquid chromatography method is described for separation and determination of ethoxylated nonylphenols. By using an amino bonded silica column with an acetonitrile-water gradient, the oligomers of ethoxylated nonylphenols with an average of 6 EO (ethylene oxide number) up to 40 EO were separated with satisfactory resolution. It was found that the partition of solutes between the stationary and mobile phases, and hydrogen bonding between salutes, solid-phase amino groups, water and acetonitrile were the main factors governing separation. The recoveries of total oligomers of nonylphenol-8 EO from a mixed emulsion with mineral oil, methyl oleate, peanut oil and the textile lubricant Blend 1 were 90.0 ± 10.2, 95.6 ± 7.9, 90.0 ± 9.5 and 107.2 ± 11.4%, respectively. The application of this method can be extended to determine non-ionic surfactants in other matrices.