While much attention has been paid to assess contamination levels of linear alkyl benzenesulfonate (LAS) surfactants in the environment, only a few papers have reported on the levels of breakdown products of LAS and coproducts. Major LAScoproducts are dialkyl tetralinsulfonates (DATS) and methyl-branched isomers of LAS (iso-LAS). A previous method (accompanying paper) based on solid-phase extraction (SPE) and liquid chromatography/mass spectrometry has been modified for monitoring theabove analytes in aqueous samples of sewage treatment plants (STPs) and in river waters. Analytes were extracted from 25, 200, and 1000 mL of respectively raw sewage, treated sewage, and river water samples by a 0.5-g Carbograph 4 SPE cartridge. Recoverystudies of some authentic short-chain LAS metabolites suggested that the SPE cartridge was able to quantitatively extract all the compounds of interest from the three types of aqueous matrixes. Under full-scan conditions, limits of detection of the method for metabolites of LAS and coproducts was set at 2 ng/L in river water. By this procedure, the concentrations in water of the analytes entering and leaving five activated sludge STPs were monthly monitored over several months. Field data indicated thatabout 50 of the metabolites of LAS coproducts were not mineralized by activated sludge treatment. More than 12 of them were dicarboxylated species. On the average, DATS metabolites amounted to more than 50 of the total analyte concentrations in STPeffluents. A short survey of the fate of persistent metabolites of LAS coproducts discharged from a STP in river water gave us some evidence that iso-LAS metabolites continued to degrade in the aquatic environment.
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