Potentiometric anion response of poly (tetrakis(p‐aminophenyl)porphyrin) film‐modified electrodes

The potentiometric response to anions of glassy carbon electrodes coated with thin unmetallated poly(tetrakis(p‐aminophenyl)porphyrin) (poly(H2(p‐TAPP))) films is examined. The polymer films are introduced onto the glassy carbon surface by constant‐potential anodic electrolysis of the porphyrin monomer from a solution of dichloromethane containing a quaternary ammonium perchlorate salt. The thickness of the film is the controlled by the electrodeposition time. Oxidized poly(porphyrin) modified electrodes exhibit near Nernstian response to iodide in the concentration range of 5 × 10−5 – 1 × 10−1 M with significant selectivity over a wide range of other anions tested. The mechanism of the electrode's iodide ion response is considered in light of its response to other redox‐active anions, and a recent literature report describing the selective iodide response of electrodes coated with electropolymerized poly(3‐methylthiophene) films. Spectroelectrochemical studies with poly(porphyrin)‐modified tin oxide electrodes are used to confirm the redox‐type response mechanism of the sensors toward iodide. The analytical limitations of using such polymer film‐modified electrodes for potentiometric ion sensing are discussed.