Ion-Selective Electrodes Based on Surface-Active Ionophores

Resonant optical second-harmonic generation (Resonant optical SHG) at the interfaces between aqueoussample solutions and liquid membranesbased on ionophores with different surface activities measured in order to investigate theionophores on-selective charge separation. As ionophoreswith different surface activitiesbut bearing the same crown ether moiety as a binding site for the Na4 -(p-octadecylbenzoateazo)phenoxymethyl-15-crown-5 (1) and4'-(p-methylbenzoateazo)phenoxymethyl-15-crown-5 (2) were synthesized. The dependence of The SHGintensities on the polarization angle of the incident laser light showed that the average molecularorientations of ionophores 1 and 2 at the liquid/liquid interface nearly equal to each other.When the concentration of Na ion in the aqueous sample solutions increased，increases in the SHG intensities observed for both membranes based on ionophores 1和2.However, the SHG intensities based on ionophore 1 were stronger，suggesting that the surface activity of ionophore 1 is higher than that of ionophore 2. the changein the phase boundary potentials of the ionophore 1-based membrane in contact with the aqueousNa - i - 1+ i - 1 ion solutions was found to be larger than that of ionophore 2. An improvement in thepotentiometric detection limit for Na - i - D1+ ion was also shown for membranes based onface-active ionophore 1. These results demonstrate that the extent of charge separation at theliquid/liquid interface, as observed by resonant SHG from primary ion complexes，is increased by using face-active ionophores。

Resonant optical second-harmonic generation (resonant optical SHG) at the interfaces between aqueous sample solutions and liquid membranes, based on ionophores with different surface activities was measured in order to investigate the influence of the surface activity of ionophores on ion-selective charge separation. As ionophores with different surface activities, but bearing the same crown ether moiety as a binding site for the NaィイD1+ィエD1 ion, 4'-(p-octadecylbenzoateazo)phenoxymethyl-15-crown-5 (1) and 4'-(p-methylbenzoateazo)phenoxymethyl-15-crown-5 (2) were synthesized. The dependence of the SHG intensities on the polarization angle of the incident laser light showed that the average molecular orientations of ionophores 1 and 2 at the liquid/liquid interface were nearly equal to each other. When the concentration of NaィイD1+ィエD1 ion in the aqueous sample solutions increased, increases in the SHG intensities were observed for both membranes based on ionophores 1 and 2. However, the SHG intensities based on ionophore 1 were stronger, suggesting that the surface activity of ionophore 1 is higher than that of ionophore 2. The change in the phase boundary potentials of the ionophore 1-based membrane in contact with the aqueous NaィイD1+ィエD1 ion solutions was found to be larger than that of ionophore 2. An improvement in the potentiometric detection limit for NaィイD1+ィエD1 ion was also shown for membranes based on surface-active ionophore 1. These results demonstrate that the extent of charge separation at the liquid/liquid interface, as observed by resonant SHG from primary ion complexes, is increased by using surface-active ionophores.