Estimation of immobilized horseradish peroxidase in a low salt concentration for an irreversible electrochemical system

Abstract

We examined the direct electron transfer of horseradish peroxidase (HRP) at HRP/carbon paste (CP)-modified electrodes under irreversible electrochemical conditions. The amount of electroactive HRP (Γ) was estimated as 2.0 × 10−9 to 3.9 × 10−9 mol, indicating that the effectiveness factor, defined as the ratio of the amount of electroactive HRP to the amount of HRP incorporated into CP, was 0.14–0.24. In the presence of potassium ferricyanide(III) (K3Fe(CN)6) and potassium hexacyanoferrate(II) (K4Fe(CN)6) as mediators, the electroactive surface area of only HRP on the HRP/CP-modified electrode was 0.0164 cm2. The theoretically calculated coverage area of electroactive HRP on the HRP/CP-modified electrode was much greater than the electroactive surface area of the CP electrode. In addition, the rate constant (k°) of the electrochemical reaction of HRP at the HRP/CP-modified electrode was 0.006 s−1 for the oxidation process.

Keywords

• Irreversible system
• Horseradish peroxidase-modified electrode
• Low salt concentration