A REAGENTLESS AMPEROMETRIC BIOSENSOR FOR HYDROGEN-PEROXIDE DETERMINATION BASED ON ASPARAGUS TISSUE AND FERROCENE MEDIATION

A new reagentless biosensor for the amperometric detection of hydrogen peroxide was developed by co-immobilisation of ground asparagus tissue (Asparagus officinalis) and ferrocene in a carbon paste matrix. The asparagus tissue acts as a source of peroxidase. Ferrocene is utilised as a mediator to facilitate efficient electron transfers between the electrode surface and hydrogen peroxide. The detection of hydrogen peroxide was based on the measurement of amperometric response due to the reduction at the electrode of ferricinium ion generated from the enzymatic reaction at 0.00 mV vs. SCE. The response characteristics and optimisation of the bioelectrode design are evaluated. The bioelectrode exhibits linear response up to a hydrogen peroxide concentration of 6 X 10(-5) M with a detection limit of 4.0 X 10(-7) M. Response times (t(90)) as low as 2 s and a relative standard deviation of replicate measurements of 1 X 10(-5) M hydrogen peroxide of 1.95% (n = 15) were achieved. The bioelectrode sensitivity decreased to 50% of the original value within 30 days of continuous use.