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Abstract
A supported liquid membrane (SLM) extraction method was developed for anionic surfactants. A porous PTFE membrane was impregnated with a water immiscible organic solvent, forming a selective barrier between the sample and the analytical instrument. With a flowing donor and a stagnant acceptor solution, an enrichment of analytes was obtained. A mixture of linear alkylbenzenesulfonate (LAS) homologues and isomers were used as model system with the components transported across the membrane as ion-pairs formed with a tertiary amine. A slow mass transfer kinetics over the membrane/acceptor interface was noted. By pumping fresh acceptor solution through the acceptor channel for 15 minutes after the enrichment and trapping the analytes subsequently on an anion exchange column, the carry-over effects could be greatly reduced. With 1 hour SLM extraction time, concentrations of LAS down to 2 μg/L could be determined in natural water samples using UV-detection.
