Determination of nonionic aliphatic and aromatic polyethoxylate surfactants in environmental aqueous samples

Nonionic surfactants of the polyethoxylate type are environmentally relevant because of their ubiquitous presence in raw and treated, municipal and industrial, wastewaters. Until today the standard methods currently used for the routine determination of nonionic surfactants in environmental matrices are cumulative methods (BIAS, CTAS, PPAS, TAS), which are poorly reliable, particularly in terms of accuracy, and do not supply any structural information on the ethoxymeric and homolog composition, as well as on the chain length of the hydrophobic moiety. This paper describes a specific analytical procedure for the simultaneous specific determination of polyethoxylate aliphatic (AE) and aromatic (APE) nonionics in aqueous matrices. The analytes were isolated from water samples by solid phase extraction with graphitized carbon black and then derivatized with 1-naphthylisocyanate (NIC). AE and APE were separated by reversed-phase HPLC combined with fluorescence detection (RP-HLPC/FL). The analytical procedure was applied to the monitoring of these two classes of surfactants in a municipal sewage treatment plant. The method allows rapid, precise and reliable determination of AE and APE in environmental samples at concentrations as low as 0.1 mg/L.