The potentiometric behavior of polymer supported metalloporphyrins as anion-selective electrodes

The potentiometric behavior of polystyrene pyridine copolymer supported manganese (III) and tin (IV) protoporphyrin IX (MnPPIX-PSP4 and SnPPIX-PSP4) was investigated. As expected, both MnPPIX-PSP4 and SnPPIX-PSP4-based membrane electrodes showed size exclusion effects on salicylate, these may be caused by a cross-linked polymer matrix which can act as an asymmetric cellulose membrane to exclude the bigger sized lipophilic anions such as salicylate. Pyridine attached to the polymer chain can influence the selectivity pattern of the aforementioned membrane electrodes as the axial ligand to the central metal of the porphyrins. The lifetimes of the polymer supported ionophore-based membrane electrodes are significantly enhanced from those of porphyrin-based electrodes and the super-Nernstian phenomenon found on Sn porphyrin-based membrane electrodes also disappeared.