CHROMATOGRAPHIC TOOLS FOR ANALYZING AND TRACKING NONIONIC SURFACTANTSIN THE AQUATIC ENVIRONMENT

This review describes the developments over the last few decades in th e routine determination of two major types of non-ionic surfactants in environmental samples, i.e. alkylphenol ethoxylates (APE) and alcohol ethoxylates (AE). Commercial mixtures of these surfactants consist of several tens to hundreds of homologues, oligomers and isomers. Theref ore, their identification and quantitation in the environment is compl icated and cumbersome. The request for more specific analytical method s has prompted a replacement of all the separate steps in traditional, usually non-chromatographic methods of analysis of AP and APE by chro matographic tools. Thus, a 100-fold gain in detection limits has been achieved. Determination of AE and APE in aqueous samples is possible a t the ppb level nowadays, when solid-phase extraction, including chrom atographic cleanup, is applied, followed by liquid chromatography (LC) . Reversed-phase LC resolves the various alkyl homologues, whereas nor mal-phase LC provides information on the ethoxylate oligomer distribut ion. Because of differences in (bio)degradation patterns observed in t he aqueous environment between AE and APE, it is recommended to analys e AE by reversed-phase LC and APE by normal-phase LC. The more sophist icated hyphenated LC-MS techniques provide full information on isomer, oligomer and homologue distribution of both AE and APE.