The potentiometric anion responses of polymeric membranes doped with various indium (111)-porphyrin structures are examined. The appropriate membranes are prepared by incorporating 1.0 wt % of the In(II1)-porphyrins in plasticized poly(viny1 chloride) films. When such membranes are incorporated within standard ion selective electrode bodies, the resulting electrodes display non-Hofmeister anion selectivity, with a particularly enhanced and super-Nernstian response to chloride. Among those porphyrins investigated, membranes doped with chloro(octaethylporphyrinato)indium( 111) yield the largest and most reproducible potentiometric anion responses. These same membrane electrodes exhibit negligible response to protons (or hydroxide) in the range of pH 4.5-9.0. When utilized as a flowinjection detector in conjunction with a protein diluenVbuffer stream, the In( 111)-porphyrinbased electrodes may be used to determine chloride levels in human serum samples.

The chemistry leading to the selective potentiometric response toward salicylate of polymer membranes doped with 5,10,15,20-tetraphenyl(porphyrinato)tin(IVl dichloride (Sn(TPPlCls) is examined via '19Sn NMR, 3H,0 uptake, spectrophotometric, and solution conductometric techniques. The response properties of ion-selective electrodes prepared with such membranes suggest a complex mechanism of anion binding within the membrane phase. In the pure organic phase, spectroscopic data indicate that salicylate binds directly to one or both axial coordination sites of Sn(IV), displacing the initial chloride ligands. In the presence of water, however, both chloride and salicylate are displaced by water molecules, resulting in a dipositively charged metalloporphyrin cation. Furthermore, conductance measurements point to the formation of salicylate-porphyrin complexes with greater than 2: 1 stoichiometry. The results of these studies are discussed in conjunction with the anomalous cationic emf response of Sn(TPPlCl,-based membranes at high concentrations of salicylate. A response mechanism is proposed which involves outer-sphere coordination of salicylate to a diaquo ligated metalloporphyrin as a key step in the observed anion extraction/equilibrium with the membrane phase.