Development of a method for the simultaneous analysis of anionic and non-ionic surfactants and their carboxylated metabolites in environmental samples by mixed-mode liquid chromatography–mass spectrometry

A new methodology capable of performing the simultaneous analysis of the main surfactants – linear alkylbenzene sulfonates (LAS), alkyl ethoxysulfates (AES), alkyl sulfates (AS), nonylphenol polyethoxylates (NPEOs) and alcohol polyethoxylates (AEOs) – and their carboxylated metabolites – sulfophenyl carboxylic acids (SPCs) and alkylphenol ethoxycarboxylates (APECs) – in environmental samples has been developed for the first time. Extraction is carried out by solid-phase extraction (SPE) and pressurized liquid extraction (PLE) from water and sediment, respectively. Identification and quantification of the target compounds is performed using a liquid chromatography–mass spectrometry (LC–MS) system equipped with an electrospray interface (ESI) operating in mixed-mode. Optimization of parameters such as pH, ionic strength, temperature and solvents has been carried out in order to obtain recoveries in the range from 70 to 107% for most homologs, while the limits of detection are 0.05–0.5 ng mL−1 in water and 1–10 ng g−1 in sediment. The proposed methodology has been applied for the simultaneous determination of all the target compounds in samples taken from aquatic ecosystems in the SW of Spain. Values for LAS, AS, AES, NPEOs and AEOs are up to 38.7, 3.0, 2.9, 5.0 and 1.2 μg L−1 in waters, and in the ranges of 1.73–12.80, 0.11–0.24, 0.02–0.59, 1.94–2.70 and 0.64–3.64 mg kg−1 in sediments, respectively. The highest concentrations of metabolites found in water are 149.6 μg L−1 of SPCs and 3.9 μg L−1 of APECs.