Highly-sensitive flow injection determination of hydrogen peroxide with a peroxidase-immobilized electrode and its application to clinical chemistry Original Research Article

A flow injection system for determination of hydrogen peroxide was constructed using a peroxidase/ferrocene-embedded carbon paste (POD-Fc-CP) electrode covered with a membrane. H2O2 was reduced bioelectrocatalytically at 100 mV (versus Ag/AgCl/sat. KCl). A Nafion®-coated cellulose acetate membrane prepared on the surface of water proved to be suitable for the covering membrane. The detection limit (signal : noise = 6) for H2O2 was 200 fmol (10 nM × 20 μl) and the response linearity was retained at least up to 25 μM. The relative standard deviation was 4.4% for 1.0 μM H2O (n = 7). The flow injection system was successfully applied to the determination of glucose and urate in serum by using the corresponding oxidase-immobilized pre-column. The detection limits were 1.5 pmol for glucose and 2 pmol for urate.