title: Microporous membrane liquid-liquid extraction coupled on-line with normal-phase liquid chromatography for the determination of cationic surfactants in river and waste water.
abstract: Membrane-based continuous liquid-liquid extraction combined on-line with normal-phase liquid chromatography is proposed for the determination of cationic surfactants in complex aqueous samples. The technique has the potential for complete automation. Selective enrichment of cationic surfactants from spiked river water and waste-water samples with simultaneous removal of matrix constituents, followed by a quantitative transfer of the extract onto a liquid chromatographic column and separation of the surfactant homologues yielding low detection limits, has been realised. The homologues of alkyldimethylbenzylammonium chloride (Dodigen 226) were chosen as model compounds in the method development. Dodigen homologues were ion-paired with heptanoic acid and extracted into chlorobutane by means of microporous membrane liquid-liquid extraction. It was thereby possible to attain an enrichment of over 250 times for one of the homologues, viz. the concentration in the organic liquid is 250 times higher than in the original sample. Detection limits for the three best-detected homologues of the mixture were in the range 0.7-5 microg/l in spiked river water samples. Ion-pair normal-phase liquid chromatography, again with heptanoic acid as counter-ion, gave the necessary separation of the surfactant homologues.
authors.affiliation: Department of Analytical Chemistry, Lund University, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Norberg
authors.forename: E
authors.initials: E
authors.lastname: Thordarson
authors.forename: L
authors.initials: L
authors.lastname: Mathiasson
authors.forename: J A
authors.initials: JA
authors.lastname: Jönsson
mesh_terms: D002412:Cations; D002853:Chromatography, Liquid / Q000379:methods*; D007220:Industrial Waste; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet; D013501:Surface-Active Agents / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D002412:Cations; D007220:Industrial Waste; D013501:Surface-Active Agents; D014874:Water Pollutants, Chemical