Simultaneous determination of anionic and nonionic surfactants in commercial laundry wastewater and anaerobic fluidized bed reactor effluent by online column-switching liquid chromatography/tandem mass spectrometry
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This study presents a new method developed for the simultaneous determination of anionic surfactant (linear alkylbenzene sulfonate – LAS, 4 homologs) and nonionic surfactant (linear alcohol ethoxylate – LAE) in commercial laundry wastewater. The surfactants were identified and quantified using online column-switching solid-phase extraction (SPE) coupled with liquid chromatography/tandem mass spectrometry (LC-MS/MS). Ten and three transitions (m/z) were identified for LAS and LAE, respectively. The detection and quantification limits were 75 and 200 μg/L for LAS, respectively, and 75 μg/L for LAE. This method was applied to the determination of the surfactants in the influent and effluent of an anaerobic fluidized bed reactor that was used for the treatment of commercial laundry wastewater. After 480 days of operation with a hydraulic retention time (HRT) of 18 h, the removal of 45.9 ± 5.6% LAS and 99.2 ± 4.3% LAE from an influent with surfactant concentrations of 26.1 ± 12.9 mg/L and 23.8 ± 6.8 mg/L, respectively, was obtained. Under these conditions, the breakage of longer-chain LAS homologs with the release of carbon units was observed with an increase in the number of shorter homolog chains. This SPE online sample treatment method is simple, fast and effective for the analysis of both surfactants. This technique is pioneering in its simultaneous measurement of two surfactant categories in anaerobic fluidized bed reactors.