Iron(III) tetra-(N-methyl-4-pyridyl)-porphyrin as a biomimetic catalyst of horseradish peroxidase on the electrode surface: an amperometric sensor for phenolic compound determinations.

The use of iron(III) tetra-(N-methyl-4-pyridyl) porphyrin (FeIIIT4MpyP) and histidine (His) in the construction of an amperometric sensor for phenolic compound determinations is reported, based on horseradish peroxidase (HRP) chemistry. The sensor was prepared by modifying a glassy carbon electrode with Nafion membrane doped with FeIIIT4MpyP and His, in a mass ratio of 1:2. The sensor presented its best performance at 50 mV vs. SCE in 0.1 mol l(-1) succinate buffer (pH = 4.0) containing 125 micromol l(-1) H2O2. Under optimized operational conditions, a linear response range from 0.6 to 6.0 micromol l(-1) was obtained with a sensitivity of 61 nA cm(-2) micromol l(-1). The detection limit for catechol determination was 0.35 micromol l(-1). The response time was less than 0.5 s. The proposed sensor presented stable responses for 100 successive determinations, while satisfactory responses were observed even after 200 measurements. The repeatability, evaluated in terms of relative standard deviation, was 4% for n = 7. The signal responses for other phenolic compounds, including those of environmental and clinical interest, were also investigated.