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

A flow injection system for determination of hydrogen peroxide was construc ted using a peroxidase/ferrocene-embedded carbon paste (POD-Fc-CP) electrod e covered with a membrane. H2O2 was reduced bioelectrocatalytically at 100 mV (versus Ag/AgCl/sat. KCl). A Nafion(R)-coated cellulose acetate membrane prepared on the surface of water proved to be suitable for the covering me mbrane. The detection limit (signal :noise = 6) for H2O2 was 200 fmol (10 n M x 20 mu l) and the response linearity was retained at least up to 25 mu M . The relative standard deviation was 4.4% for 1.0 mu M H2O (n = 7). The fl ow injection system was successfully applied to the determination of glucos e and urate in serum by using the corresponding oxidase-immobilized pre-col umn. The detection limits were 1.5 pmol for glucose and 2 pmol for urate. ( C) 2000 Elsevier Science B.V. All rights reserved.