Determination of Nonionic Polyethoxylate Surfactants in Environmental Waters by Liquid Chromatography/Electrospray Mass Spectrometry

Abstract

A very sensitive and specific analytical procedure for determining nonionic polyethoxylate surfactants, such as aliphatic ethoxylate alcohols (AEOs) and nonylphenol polyethoxylates (NPEOs), in aqueous environmental samples using electrospray liquid chromatography/mass spectrometry is presented. This procedure involves passing 10, 100, 1000, and 4000 mL of raw sewage, treated sewage, river water, and drinking water samples, respectively, through a 1-g graphitized carbon black (GCB) extraction cartridge. By exploiting the presence of positively charged active centers on the GCB surface, we succeeded in isolating AEOs and NPEOs from both surfactants and biointermediates acidic in nature by differential elution. Recoveries of the analytes ranged between 85 and 97%, irrespective of the aqueous matrix in witch they were dissolved. Chromatography was adjusted for eluting all the oligomers of NPEO and of the various AEO homologues as single peaks. This chromatographic condition enhances detection levels and samples quantification of the analytes. The limit of detection (signal-to-noise ratio=3) was estimated to be about 20 pg/component injected into the column or 0.6, 0.02, 0.002, and 0.0002 μg/L of each analyte in the influents and effluents of sewage treatment plants, river water, and drinking water, respectively. This procedure was employed for assessing the concentrations of the analytes in seven influent and seven effluent samples of three mechanical-biological treatment plants. The analysis of a municipal water sample revealed the presence of the analytes at parts-per-trillion levels