A new film for the fabrication of an unmediated H 2O 2 biosensor

Abstract

A novel and stable film made from polyethylene glycol (PEG) on pyrolytic graphite (PG) electrode was presented in this paper for incorporating horseradish peroxidase (HRP) to study the direct electrochemistry of the enzyme. In PEG film, HRP showed a thin-layer electrochemistry behavior. The apparent standard potential ( E°′) was −0.379 V versus SCE at pH 7.2. Moreover, the PEG–HRP modified electrode exhibited excellent electrocatalytical response to the reduction of H 2O 2 with a calibration range between 2.0×10 −6 and 6.0×10 −4 M and a good linear relation from 2.0×10 −6 to 1.0×10 −4 M, on which an unmediated H 2O 2 biosensor was based. The detection limit of 6.7×10 −7 M was estimated when the signal-to-noise ratio was 3. The relative standard deviation (R.S.D.) was 4.7% for six successive determinations at a concentration of 4.0×10 −5 M. The apparent Michaelis–Menten constant ( K m app) of the sensor was found to be 1.38 mM. Epinephrine, dopamine, and ascorbic acid did not interfere with the sensitive determination of H 2O 2.