PEROXIDASE-BASED AMPEROMETRIC SENSOR OF HYDROGEN-PEROXIDE GENERATED IN OXIDASE REACTION - APPLICATION TO CREATININE AND CREATINE ASSAY

Peroxidase (POD) was entrapped on a ferrocene (Fc)-embedded carbon pas te (CP) electrode with a dialysis membrane to construct a POD-Fc-CP el ectrode for the reductive amperometric determination of hydrogen perox ide (H2O2). The electrode allowed the H2O2 detection down to 10 nM (un der stirring), with a linear relation up to 15 mu M, and without chang e of the response over one month. On the other hand, a plastic-formed carbon (PFC) electrode can donate electrons to POD without any specifi c mediator. The POD-entrapped PFC electrode produced a relative curren t density of 24 % compared with the POD-Fc-CP electrode. The reductive detection of H2O2 with the POD-Fc-CP electrode was applied to the det ermination of creatinine and creatine in serum and urine using sarcosi ne oxidase, creatine amidinohydrolase, and creatinine amidohydrolase a s the reagents. The significance of the membrane-covered POD-Fc-CP ele ctrode in the coupling of the oxidase reaction is also discussed.