Characterization of carbon paste electrodes modified with manganese based perovskites-type oxides from the amperometric determination of hydrogen peroxide

This work proposes the amperometric determination of hydrogen peroxide reduction and oxidation as a tool for the characterization of La(1-x)A(x)MnO(3) perovskites dispersed in a graphite composite electrode (carbon paste electrode, CPE). The catalytic activity of perovskites towards the oxidation and reduction of hydrogen peroxide is highly dependent on the nature of the A cation and on the temperature and time of calcination employed during the synthesis. Therefore, the selection of the optimal synthesis conditions to obtain the best catalytic activity towards hydrogen peroxide can be performed from amperometric determinations. We also report the analytical application of the perovskite modified CPE through the quantification of hydrogen peroxide in two real samples. Some preliminary results about the usefulness of La0.66Sr0.33MnO3-CPE to develop a glucose biosensor by incorporation of the enzyme glucose oxidase (GOx) within the electrode are also reported. The difference in sensitivity to glucose at CPE-GOx and CPE-La0.66Sr0.33MnO3-GOx (11.9 mu Amol(-1) L and 158.1 mu A mol(-1) L, respectively), clearly demonstrate the advantages of the association of the biocatalytic activity of GOx and the catalytic activity of perovskites towards hydrogen peroxide oxidation/reduction, and opens the doors to the development of new sensors for other important bioanalytes. (C) 2009 Elsevier B. V. All rights reserved.