Ion exchange between divalent counterions in anionic micellar solution

The ion exchange between divalent cations in anionic micellar systems were investigated by a fluorescence quenching technique using the anionic ruthen ium complex RuL34- (L = 4, 4'-dicarboxy-2,2-bipyridine) as an extramicellar probe and the N,N'-dimethyl-4,4'-bipyridinium ion (MV2+) as the quencher. Competitive ion exchange at the micellar surface between the divalent quenc her counterion (MV2+) and the divalent hexamethylethylenediammonium (HED2+) counterion can be adequately described with a simple pseudophase ion-excha nge formalism. The counterion exchange selectivity coefficients are K-MV/HE D = 1.3 and 1.4 for HED-decyl sulfate [HED(DeS)(2)] and HED-dodecylsulfate [HED(DS)(2)] micelles, respectively. These results show that the MV2+ catio n only slightly more strongly bound to the micelle aggregates than the HED2 + cation. (C) 1999 Elsevier Science B.V. All rights reserved.