Electrochemical studies on polysorbate‐20 (Tween 20)‐entrapped haemoglobin and its application in a hydrogen peroxide biosensor

Haemoglobin (Hb) was entrapped in polysorbate 20 and then modified on a pyrolytic graphite electrode. Electrochemical studies revealed that a pair of stable and well‐defined redox peaks attributed to the direct redox reaction of Hb could be observed in a phosphate buffer solution (pH 6.0). The anodic and cathodic peaks were located at −236 and −316 mV (versus a saturated calomel reference electrode) separately. The formal potential, E 0 ′, was linearly varied with pH in the range from 3.0 to 10.0 with a slope of −48.0 mV·pH −1 . Moreover, the protein was capable of catalysing the reduction of H 2 O 2 . Accordingly, an unmediated biosensor for H 2 O 2 was prepared with a linear range from 8.0×10 −7 to 1.0×10 −3 M. This biosensor exhibited good stability, sensitivity and reproducibility.