Determination of linear alkylbenzenesulfonates in wastewater treatment plants and coastal waters by automated solid-phase extraction followed by capillary electrophoresis–UV detection and confirmation by capillary electrophoresis–mass spectrometry

Abstract

Linear alkylbenzenesulfonates (LASs) were determined in wastewaters and coastal waters by solid-phase extraction, using two different sample preparation protocols depending on the sample treated, followed by capillary electrophoresis and ultraviolet detection (CE–UV). The linear range of the proposed method varied from 3 to 53 and from 25 to 495 μg/l, depending on the compound, with a limit of detection of 1 μg/l when 250 ml of coastal water was preconcentrated. [M−H] − ions were used for CE–MS confirmation after quantification by CE–UV. CE–MS diagnostic ions were the same ones used in LC–electrospray (ESI) MS and corresponded to m/ z 297, 311, 325 and 339 for C 10, C 11, C 12 and C 13 LASs, respectively. LASs were determined in wastewater samples of the influent and effluent of three wastewater treatment plants (WWTPs), two of them using biological treatment with secondary settlement and receiving mainly domestic wastewaters whereas one of the plants was operated with physicochemical treatment and received mainly industrial wastewaters. LASs were also analyzed in two samples from coastal waters of the bay of Cadiz (Spain) receiving untreated domestic effluents. All samples were also analyzed by LC–ESI-MS and the results are compared with the CE–UV method developed in this work. The concentration levels of total LASs varied from 988 to 1309 μg/l in the influents of WWTPs, whereas in the effluents the concentrations varied from 136 to 197 μg/l. The levels of LASs in coastal wastewaters of the bay of Cadiz varied from 739 to 911 μg/l, indicating that the wastewaters discharged into the bay did not undergo any treatment at all.