Highly sensitive determination of hydrogen peroxide and peroxidase with tetrathiafulvalene-based electrodes and the...

Redox mediators enable an efficient electron transfer between redox enzymes and the electrochemical surface of amperometric sensors. A stable and highly sensitive signal was obtained using a tetrathiafulvalene (TTF)-modified graphite electrode. In the presence of horseradish peroxidase (HRP), hydrogen peroxide (H2O2) was monitored with a detection limit of 7 nM at a potential of +20 mV versus a saturated calomel electrode (SCE). With a constant concentration of H2O2, the detection limit for HRP was found to be 150 pM. The accuracy of consecutive measurement of HRP in flow-through systems was improved by short-time polarizing the TTF-modified graphite electrode at +100 mV versus Ag/AgCl/3 M KCl. Using the TTF-modified graphite electrode in an immuno-sandwich approach, rabbit-immunoglobulin G was monitored in the range 5-100 ng/ml.