A New Composition for Co(II)-porphyrin-based Membranes Used in Thiocyanate-selective Electrodes

Abstract

In the present paper, the potentiometric response characteristics of ametalloporphyrin-based electrode in o-nitrophenyloctylether (o-NPOE) plasticizedpolyvinyl chloride (PVC) membrane are presented for a set of monovalent anions. Asmembrane ionophore, 5,10,15,20-tetrakis-(4-methoxyphenyl)-porphyrin-Co(II)(CoTMeOPP) was used. To establish the optimum composition of the membrane, differentmolar percents of cationic derivative (mol.% relative to ionophore) were used. Electrodesformulated with membranes containing 1 wt.% ionophore, 66 wt.% o-NPOE, 33 wt.% PVC(plasticizer: PVC = 2:1) and the lipophilic cationic derivative (35 mol%) are shown toexhibit high selectivity for thiocyanate with a near-Nernstian slope in the workingconcentration range of 1.0×10−1–1.0×10−5 M, with a good stability in time.

Keywords

• metalloporphyrins
• thiocyanate
• anion-selective electrode
• near-Nernstian slope.