Determination of nonylphenol ethoxylate oligomers by liquid chromatography–electrospray mass spectrometry in river water and non-ionic surfactants

Liquid chromatography–electrospray ionization mass spectrometry (LC–ESI-MS) for the quantitative determination of five nonylphenol ethoxylate (NPE) oligomers in river water was described. These NPE oligomers were separated on a poly(vinyl alcohol) gel column using acetonitrile–30 mM ammonium acetate as the mobile phase followed by ESI-MS detection without any sample concentration steps. The sample was only filtered using the disposable filter and the aliquot (100 μl) of this sample was injected into the LC–ESI-MS system. All NPE oligomers were detected using the [M+NH4]+ ion. Detection limits ranged from 160 pg/ml (NPE4) to 240 pg/ml (NPE2), repeatability and reproducibility ranged from 4.2% (NPE2) to 6.2% (NPE6) and from 7.4% (NPE5) to 9.8% (NPE6).