Determination of linear alkylbenzene sulfonates and their polar carboxylicdegradation products in sewage treatment plants by automated solid-phase extraction followed by capillary electrophoresis-mass spectrometry

Linear alkylbenzene sulfonates (LAS) were determined by solid-phase extract ion (SPE), followed by capillary electrophoresis and mass spectrometry dete ction (CE-MS). The linear range of the proposed method varied from 33 to 31 6 and from 215 to 2057 mug L-1, depending on the compound, with limits of d etection ranging from 4.4 to 23 mug L-1 when 200 ml of wastewater were prec oncentrated. The analysis and confirmation of the polar carboxylic metaboli tes of LAS, the sulfophenyl carboxylic acids (SPC) was also achieved, and t heir presence was detected in both, influent and effluents of the sewage tr eatment plant (STP). [M - H](-) ions were used for CE-MS confirmation and q uantification. CE-MS diagnostic ions were the same ones used in LC-electros pray (ESI)-MS and corresponded to m/z 297, 311, 325 and 339 for C10LAS, C11 LAS, C12LAS and C13LAS, respectively. For SPC identification, diagnostic io ns corresponded to m/z 215 to 369 (with 14 mass unit steps) for C2 to C13SP C, respectively. LAS were determined in wastewater samples of the influent and effluent of three sewage treatment plants (STP), two of them using biol ogical treatment with secondary settlement and receiving mainly domestic wa stewater whereas one of the plants was operated with physicochemical treatm ent and received mainly industrial wastewater. The concentration levels of total LAS varied from 1000 to 1900 mug L-1 in the influents of STP, whereas in the effluents the concentrations varied from 125 to 360 mug L-1.