ALKALINE-PHOSPHATASE ASSAY USING A REDOX PROCATIONIC LABELED SUBSTRATE AND A RENEWABLE NAFION-LOADED CARBON-PASTE ELECTRODE

The indirect electrochemical determination of alkaline phosphatase was achieved with a detection limit of 2 Ul(-1) at a fresh surface of a r enewable Nafion-loaded carbon paste electrode, without preconditioning . [N-ferrocenoyl]-4-aminophenyl phosphate was used as substrate and th e enzyme reaction proceeded for 15 min in Tris buffer at pH 9.0. [N-fe rrocenoyl]-4-aminophenol was thus generated, which was further preconc entrated at the modified carbon paste electrode during a 5 min accumul ation step in neutral medium. A potential of 0.35 V was applied during this step, and so the substituted phenol was irreversibly entrapped a s a ferrocenium salt within Nafion before being detected by square wav e voltammetry.