IRON(III)-SELECTIVE MEMBRANE POTENTIOMETRIC SENSOR BASED ON 5,10,15,20-TETRAKIS-(PENTAFLUOROPHENYL)-21H,23H-PORPHYRIN

A new PVC membrane electrode for Fe3+ ions based on 5,10,15,20-tetrakis (pentaflurophenyl)-21H,23H-porphyrin as membrane carrier was prepared. The sensor exhibits a super-Nernstian slope of 25.0 ± 0.5 mV per decade over a 1.0 × 10-4–1.0 × 10-6 M concentration range. It has a response time of about 10 s and can be used for at least 8 weeks without any divergence in potentials. The proposed sensor revealed very good selectivities for Fe3+ over a wide variety of other cations over a pH range 3–4. It was applied to the direct determination of iron in tap water samples and, as an indicator electrode, in potentiometric titrations of Fe3+ ion. The electrode was also successfully applied to the speciation of iron in aqueous solutions.