AbstractsChemistry

The ability of surfactant micellar aggregates to enhance collisional quenching between a model cation analyte, copper (II) ion, and two fluorescent probes, phenosafranin and N-methylacridone (NMA), was studied. The intensity of the fluorescence emission observed from these two probe molecules was monitored as a function of added copper (II) ion quencher and the data evaluated in terms of the Stern-Volmer equation in three anionic surfactant micellar systems (sodium decylsulfate (NaDS), sodium dodecylsulfate (SDS) and sodium tetradecylsulfate (NaTDS)). The presence of these anionic micellar systems enhanced the Stern-Volmer quenching constant, K_SV, relative to that observed in water alone (by a factor of ca. 80 for SDS as the micelle and NMA as fluorescent probe). The SDS micelle system appeared to be best in terms of the enhancement factor observed and the reproducibility of the results relative to NaDS or NaTDS. Temperature was found to have only a moderate effect on the K_SV values. While the effect of the luminescent probe concentration upon the K_SV value was negligible, lower signal/noise levels and hence lower limits of detection were attained as the concentration of the probe molecule was increased. A detection limit of 9.3 x 10<super>-6</super> M Cu<super>2+</super> was obtained for the system in which NMA was the probe molecule in the presence of 10.0 mM SDS surfactant molecules. A major limitation of this approach is that many other cations will interfere since they also quench these probe molecules. For real world samples, the use of micelle enhanced fluorescence quenching as a method for detection of cations will be limited to that for indirect detection following HPLC or CE separation of those analytes.