title: Influence of organic matter type and medium composition on the sorption affinity of C12-benzalkonium cation.
abstract: We used the 7-μm polyacrylate ion-exchange SPME fibers to investigate C12-benzalkonium sorption to 10 mg/L natural organic matter at concentrations well below the cation-exchange capacity. C12-BAC sorption at constant medium conditions differed within 0.4 log units for two humic acids (Aldrich, Leonardite) and peat (Sphagnum, Pahokee), with similar nonlinear sorption isotherms (KF ∼ 0.8). Sorption to the SPME fibers and Aldrich humic acid (AHA) was reduced at both low pH and high electrolyte concentration, and reduced more strongly by Ca²⁺ compared with Na⁺ at similar concentrations. Sorption isotherms for AHA (5-50-500 mM Na⁺, pH 6) was modeled successfully by the NICA-Donnan approach, resulting in an intrinsic sorption coefficient of 5.35 (Caq = 1 nM). The NICA-Donnan model further explained the stronger specific binding of Ca²⁺ compared to Na⁺ by differences in Boltzmann factors. This study provides relevant information to interpret bioavailability of quaternary ammonium compounds, and possibly for other organic cations.
authors.affiliation: Institute for Risk Assessment Sciences (IRAS), Utrecht University, Yalelaan 104, 3584 CM Utrecht, The Netherlands. y.chen@uu.nl
authors.forename: Yi
authors.initials: Y
authors.lastname: Chen
authors.forename: Joop L M
authors.initials: JL
authors.lastname: Hermens
authors.forename: Steven T J
authors.initials: ST
authors.lastname: Droge
mesh_terms: D000327:Adsorption; D001548:Benzalkonium Compounds / Q000737:chemistry*; D002412:Cations / Q000737:chemistry; D006812:Humic Substances; D006863:Hydrogen-Ion Concentration; D007474:Ion Exchange; D008956:Models, Chemical; D044003:Sphagnopsida
chemical_list: D001548:Benzalkonium Compounds; D002412:Cations; D006812:Humic Substances