CARBON-PASTE ELECTRODE INCORPORATED WITH COBALT(II) OCTAETHOXYPHTHALOCYANINE FOR THE AMPEROMETRIC DETECTION OF HYDROGEN-PEROXIDE

A hydrogen peroxide sensing electrode was prepared by incorporating co balt(II) octaethoxyphthalocyanine [CoPc(OEt)(8)] into a carbon paste ( CP) matrix. The CoPc(OEt)(8)-modified electrode could oxidize hydrogen peroxide at lower potentials than a CP electrode with unsubstituted c obalt phthalocyanine (CoPc). In addition, the CoPc(OEt)(8)-based syste m showed a high stability; the electrode response to 10 mM hydrogen pe roxide did not decrease for over 6 h, whereas the hydrogen peroxide re sponse from the CoPc-modified electrode reduced to half the initial va lue within 2 h. The CoPc(OEt)(8), which is a paraffin oil soluble deri vative of CoPc, incorporated into the bulk of the CP diffused towards the electrode surface so as to renew the electrode surface, and this r esulted in the high stability of the CoPc(OEt)(8)-modified electrode. The electrode was used as the transducer for an L-lactate-sensing enzy me sensor; the sensor could be used for more than 4 weeks and 400 assa ys.