STRIPPING MEASUREMENTS OF HYDROGEN-PEROXIDE BASED ON BIOCATALYTIC ACCUMULATION AT MEDIATORLESS PEROXIDASE CARBON PASTE ELECTRODES

Biocatalytic accumulation, followed by chronoamperometric detection, is shown to greatly enhance the sensitivity of mediatorless biosensing of hydrogen peroxide at horseradish peroxidase (HRP)/carbon paste bioelectrodes. The mixed carbon paste, with its close proximity between the biocatalytic and graphite sensing sites, promotes the mediatorless accumulation of the oxidized form of HRP. Hence, a 28-fold enhancement of the response for 10 muM hydrogen peroxide is obtained following 3-minute preconcentration. The relative standard deviation (surface-to-surface) at the 10 muM level is 3.3%. The effect of experimental variables, such as the preconcentration time, measuring potential, or paste composition, are explored. Analogous observations are reported for tissue (horseradish root)-based carbon pastes, for mediated HRP detection, and for monitoring of organic peroxides. Future prospects of the bioamplification approach are discussed.