title: Analyzing freely dissolved concentrations of cationic surfactant utilizing ion-exchange capability of polyacrylate coated solid-phase microextraction fibers.
abstract: A 7-μm polyacrylate (PA) coated fiber was successfully employed to determine freely dissolved concentrations of cationic surfactants by solid-phase microextraction (SPME) and utilizing the capability of the PA-coating to sorb organic cations via ion-exchange at carboxylic groups. Measured fiber-water partitioning coefficients (K(fw)) were constant below a fiber loading of 2mmol per liter polyacrylate, allowing for simple and accurate analysis in a concentration range that is relevant from a risk assessment point of view. Ion-exchange was confirmed to be the main sorption mechanism because of a decreasing K(fw) with either higher CaCl(2) concentrations or lower pH, and maximum fiber uptake at the polyacrylate cation-exchange capacity (CEC, at 30mmol/L PA). Fiber-water sorption isotherms were established in various aqueous media in toxicological relevant concentrations. The developed SPME method has a high potential for application in ecotoxicological studies, as demonstrated in sorption studies with humic acid in different electrolyte solutions at aqueous concentrations down to the sub nM range. Cationic surfactant sorption affinities for humic acid also depend on medium composition but are orders of magnitude higher than to the PA fiber on a sorbent weight basis.
authors: Institute for Risk Assessment Sciences, Utrecht University, Yalelaan 104, 3584 CM Utrecht, The Netherlands. y.chen@uu.nl
authors: Yi
authors: Y
authors: Chen
authors: Steven T J
authors: ST
authors: Droge
authors: Joop L M
authors: JL
authors: Hermens
mesh_terms: D000180:Acrylic Resins / Q000737:chemistry*; D000327:Adsorption; D002122:Calcium Chloride / Q000737:chemistry; D002412:Cations / Q000737:chemistry; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D006812:Humic Substances / Q000032:analysis; D007474:Ion Exchange; D007700:Kinetics; D009757:Nylons / Q000737:chemistry; D000644:Quaternary Ammonium Compounds / Q000737:chemistry*; D012965:Sodium Chloride / Q000737:chemistry; D052617:Solid Phase Microextraction / Q000295:instrumentation*; D013501:Surface-Active Agents / Q000737:chemistry*
chemical_list: D000180:Acrylic Resins; D002412:Cations; D004129:Dimethylpolysiloxanes; D006812:Humic Substances; D009757:Nylons; D000644:Quaternary Ammonium Compounds; D013501:Surface-Active Agents; C085707:poly(dimethylsiloxane)-polyamide copolymer; D012965:Sodium Chloride; C006903:carbopol 940; D002122:Calcium Chloride