Theoretical and experimental study of the biamperometry for irreversible redox couple in flow system

The biamperometry for the direct determination of irreversible redox analytes in flow system has been proposed based on coupling two independent and irreversible couples to form the biamperometric detection, scheme. In this work, the method is studied both theoretically and experimentally. Equations describing the current-voltage characteristics and the current-concentration relationship are presented. The influence of the applied potential difference (DeltaE) and the half-wave potential difference (DeltaE(1/2)) between two irreversible couples on the method are discussed. It shows that small DeltaE(1/2) is favorable to construct the biamperometric detection system and to achieve high sensitivity and selectivity. Increasing DeltaE leads to an increase in sensitivity. This is, however, accompanied by a decrease in selectivity and signal-to-noise ratio. To construct the biamperometric scheme for the irreversible systems with large DeltaE(1/2), two approaches, adjusting acidity of supporting electroyte or adding new irreversible couple, are proposed by taking uric acid/platinum oxide and phenol/permanganate systems as examples. Uric acid and phenol are, respectively, detected in a flow injection system with a biamperometric detector. (C) 2002 Elsevier Science B.V. All rights reserved.