Highly selective first generation glucose biosensor based on carbon paste containing copper and glucose oxidase

A highly selective electrochemical glucose biosensor based on the dispersio n of copper microparticles and glucose oxidase into a carbon paste matrix i s described. Copper offers a very efficient and preferential electrocatalyt ic activity towards the reduction of enzymatically generated hydrogen perox ide. Careful evaluation of the influence of copper content in the paste on the sensitivity and selectivity of the biosensor was performed, and 1.2 % w /w copper was selected as the optimum. Hence, the strong electrocatalytic e ffect of copper towards hydrogen peroxide allows for a fast and remarkably selective glucose quantification at -0.100 V No interference was observed e ven in the presence of large excess of ascorbic acid (up to 3.5 x 10(-3) M) , uric acid (up to 5.0 x 10(-4) M, 8.3 mg %) or acetaminophen (up to 7.4 x 10(-4) M). The detection limit was 150 muM, and the response was linear up to 6.0 x 10(-3) M. When stored dried at 4 degreesC, the sensor showed almos t no change in the analytical performance after operating for 30 days. Cali bration plots performed with glucose solutions prepared in human blood seru m samples containing undetectable glucose level, showed no appreciable diff erences with those obtained using pure glucose standard solutions, The usef ulness of the bioelectrode for direct glucose quantification in human blood serum matrices is also discussed.