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 paste (CP) electrode with a dialysis membrane to construct a POD-Fc-CP electrode for the reductive amperometric determination of hydrogen peroxide (H2O2). The electrode allowed the H2O2 detection down to 10 nM (under stirring), with a linear relation up to 15 mu M, and without change of the response over one month. On the other hand, a plastic-formed carbon (PFC) electrode can donate electrons to POD without any specific mediator. The POD-entrapped PFC electrode produced a relative current 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 determination of creatinine and creatine in serum and urine using sarcosine oxidase, creatine amidinohydrolase, and creatinine amidohydrolase as the reagents. The significance of the membrane-covered POD-Fc-CP electrode in the coupling of the oxidase reaction is also discussed.