Improvement of the performance of H2O2 oxidation at low working potential by incorporating TTF-TCNQ into a platinum wire electrode for glucose determination

A micro-biosensor was constructed by incorporating the organic conducting s alt tetrathiafulvalene-tetracyanoquinodimethane (TTF-TCNQ) into a platinize d platinum (Pt) wire and further covering with the electrochemical polymeri cal heteropolypyrrole film, in which glucose oxidase (GOx) was entrapped. T he enzyme electrode can sensitively determine glucose at a low working pote ntial, mainly based on the oxidation of H2O2. The incorporated TTF-TCNQ can significantly improve the oxidation of H2O2 on the electrode, although a p art of the TTF-TCNQ functions as a mediator. Compared with the same electro de prepared without TTF-TCNQ incorporated, the TTF-TCNQ modified electrode had better performance characteristics at a working potential of 200 mV (ve rsus SCE). The response time to 90% of the steady value was shortened from about 40 s to less than 10 s, the lower limit of the linear response was gr eatly extended from about 1.6 mM to 10 mu M, the linear range was shifted f rom 1.6-10.0 to 0.01-5 mM and the sensitivity was increased from about 1 to 1.5 mu A/mM. The electrode was quite stable. For continuous operation, the electrode could work for about 5 weeks and only lost 60% of its original s ensitivity. Stored at 4 degrees C for intermittent determinations, the elec trode kept 80% sensitivity for over 6 months. Due to covering the electrode with a non-conductive heteropolypyrrole film, ascorbate, urate and 4-aceta midophenol caused only negligible current response at an applied potential of 200 mV. (C) 1999 Elsevier Science S.A. All rights reserved.