• Yadav, Dharmendra Kumar
• Marken, Frank
• Ganesan, Vellaichamy
• Azad, Uday Pratap

Abstract

Four polypyridyl redox catalysts Fe(bp) 3 2+ , Fe(ph) 3 2+ , Fe(dm) 3 2+ , and Fe(tm) 3 2+ (with bp, ph, dm, and tm representing 2,2′-bipyridine, 1,10-phenanthroline, 4,4′-dimethyl-2,2′-bipyridine, and 3,4,7,8-tetramethyl-1,10-phenanthroline, respectively) are investigated for the electrocatalytic oxidation of three analytes (nitrite, arsenite, and isoniazid). The poly-pyridyl iron complex is exchanged into a Nafion film immobilized on a glassy carbon electrode, which is then immersed in 0.1 M Na 2 SO 4 . Cyclic voltammetry is employed for the evaluation of the mechanism and estimation of kinetic parameters. The electrocatalytic behaviour going from low to high substrate concentration is consistent with the Albery-Hillman cases of "LEty" switching to "LEk" (changing from the first order in the substrate to half order in the substrate), denoting a process that occurs in a reaction zone close to the electrode surface with diffusion of charge (from the electrode surface into the film) and of anionic or neutral analyte (from the Nafion-solution interface into the film). The relative hydrophobicity of the iron polypyridyl catalyst within the film is shown to affect both the diffusion of charge/electrons and analyte within the film with Fe(tm) 3 2+ providing the mildest catalyst. All three analytes, nitrite, isoniazid, and arsenite, exhibit linear calibration ranges beneficial for analytical applications in the micro-molar to the milli-molar range.

Topics

• impedance spectroscopy
• surface
• Carbon
• iron
• cyclic voltammetry