Simultaneous extraction and determination of anionic surfactants in waters and sediments

Abstract

A new method has been developed for the simultaneous determination of the most frequently used anionic surfactants – linear alkylbenzene sulfonates (LAS), alkyl ethoxysulfates (AES) and alkyl sulfates (AS) – in aqueous and sediment samples. Preconcentration and purification of water samples are carried out by means of solid-phase extraction (SPE). The efficiency of two different extraction methods for the analysis of sediments – Soxhlet extraction and pressurized liquid extraction (PLE) – has been compared. Identification and quantification of the target compounds is performed using a liquid chromatography – mass spectrometry (LC–MS) system equipped with an electrospray interface (ESI) in negative ion-mode. Homologue recoveries are 85–123% for SPE, 94–112% for Soxhlet extraction and 81–125% for PLE in the case of LAS, and 60–94% for SPE, 61–109% for Soxhlet extraction and 55–99% for PLE in the case of AES, whereas the limits of detection are 0.1–0.5 ng ml −1 in water and 1–5 ng g −1 in sediment. This method has been applied to the determination of anionic surfactants in the Guadalete estuary (SW Spain), and LAS concentration levels from 538 to 1014 ng g −1 in sediments and from 25.1 to 64.4 ng ml −1 in waters have been found. AES values from 168 to 536 ng g −1 in sediments and from 4.5 to 11.9 ng ml −1 in waters are reported for the first time in European rivers.