Peroxidase-modified carbon paste microelectrode as amperometric FI-detector for peroxides in partial aqueous media

Biosensor characteristics of peroxidase‐lactitol‐modified carbon paste microclectrodes have been evaluated in aqueous and partial aqueous media (H2O–10% v./v. CH3OH and H2O–10% v./v. CH3CN), for hydrogen peroxide and 2‐butanone peroxide amperometric detection, using a flow injection system. The activity of the investigated peroxidases (horseradish and fungal peroxidase from Arthromyces ramosus) was higher for hydrogen peroxide than for 2‐butanone peroxide, irrespective of the solvent composition. For both peroxidases, the microelectrodes' sensitivity, estimated from the slopes of the linear domains as well as calculated from the Eddie‐Hofstee plots decreased in the sequence: H2O > H2O–10% v./v. CH3CN > H2O–10% v./v. CH3OH. It is suggested that this behavior was due to the difference between the polarity and other physical properties, such as kinematic viscosity and dielectric constant of the nonaqueous solvents.