Use of polypyrrole film containing Fe(CN)63- as pseudo-reference electrode: application for amperometric biosensors
Résumé
A polypyrrole-containing Fe(CN)63− modified electrode was prepared by anodic electropolymerization at 0.8 V versus SCE of an aqueous solution containing only pyrrole and K4Fe(CN)6. The concentration of electroactive Fe(CN)63− ions in the polymer was found to be 30 times higher than that of the ferrocyanide ions in the electrolytic solution. Furthermore the Fe(CN)63−/Fe(CN)64− redox system exhibited a high degree of reversibility. These properties made it possible to use the modified electrode as a pseudo-reference in a weakly polarized two-electrode device for the design of amperometric biosensors involving NAD-dependent dehydrogenases. The assay of d-lactic acid was taken as an example using d-lactate dehydrogenase and diaphorase. The sensitivity of the biosensor, i.e. 20 μA mM−1 cm−2, was similar to that in previous studies. The modified electrode exhibited a relatively stable potential for currents lower than 100 nA and had an operating life of more than 2 months.