| Abstract
| - The authors present an automated flow injection analysis(FIA) system for the determination of low levels of anionicsurfactants in river water and wastewater. The systemuses especially constructed tubular flow-through ion-selective electrodes (ISEs) as potentiometric sensors andon-line preconcentration techniques. The anionic surfactant ISEs employed are of the all-solid-state type with aplasticized PVC membrane. They show a general responseto anionic surfactants with a lower limit of linear responseof ∼10-5 M, when used in direct determinations. However, their specificity is limited, which hampers theirdirect use with environmental samples. Therefore, the FIAsystem presented here includes a solid-phase extractionprocedure for purification and preconcentration of analytes. Breakthrough curves were constructed to characterize different sorbents and different eluents were tested tooptimize the preconcentration process. The FIA systemwas first applied to the determination of different typesof anionic surfactant standards. Potentially interferingsubstances such as chloride, nitrate, and nonionic surfactants were checked to verify that they did not interfereon the response of the system. Concentrations of ∼10-7M (0.03 ppm) of sodium dodecyl sulfate could be detected in the nonlinear response region when 3 mL ofsample was preconcentrated and eluted with 50 μL of a75% acetonitrile/water (v/v) solution. Precision was 2%RSD (n = 31) for a 1 × 10-6 M sodium dodecyl sulfatestandard solution and the sample throughput was 10 h-1.The FIA system was then used for the determination oftotal anionic surfactants in river water and wastewater.
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