Peroxidase‐based amperometric sensor of hydrogen peroxide generated in oxidase reaction: Application to creatinine and creatine assay

Abstract 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 (H 2 O 2 ). The electrode allowed the H 2 O 2 detection down to 10 nM (under stirring), with a linear relation up to 15 μM, 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 H 2 O 2 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.