Self-driven coulometry of ethanol, D-glucose and D-fructose using ubiquinone-dependent dehydrogenase reactions

Development Perspective of Bioelectrocatalysis-Based Biosensors

Bioelectrocatalysis provides the intrinsic catalytic functions of redox enzymes to nonspecific electrode reactions and is the most important and basic concept for electrochemical biosensors. This review starts by describing fundamental characteristics of bioelectrocatalytic reactions in mediated and direct electron transfer types from a theoretical viewpoint and summarizes amperometric biosensors based on multi-enzymatic cascades and for multianalyte detection. The review also introduces prospective aspects of two new concepts of biosensors: mass-transfer-controlled (pseudo)steady-state amperometry at microelectrodes with enhanced enzymatic activity without calibration curves and potentiometric coulometry at enzyme/mediator-immobilized biosensors for absolute determination.

Potential-step coulometry of D-glucose using a novel FAD-dependent glucose dehydrogenase

This paper describes the construction and characterization of a batch-type coulometric system for the detection of D-glucose using a novel FAD-dependent glucose dehydrogenase. In order to overcome the problem of interferents, such as ascorbate and urate, a potential-step method was proposed to separate the electrolysis reactions of interferents and D-glucose by selecting a mediator possessing an appropriate formal potential. The rapid oxidative consumption of the interferents proceeded in the first step, whereas the mediator and glucose remained reduced. In the second step, the mediator was immediately oxidized, and subsequent bioelectrocatalytic oxidation of D-glucose occurred with the aid of aldose 1-epimerase. In this study, potassium octacyanomolybdate (IV) with a formal potential of 0.6 V vs. Ag|AgCl was chosen as a mediator, and the first and second electrolysis potentials were set at 0.4 V and 0.8 V, respectively, by considering the heterogeneous electron-transfer kinetics and the potential window. The background-corrected response in charge corresponded to 99+/-2 % efficiency in terms of the amount of D-glucose.

Coulometric titration of D(+)-glucose using its enzymatic oxidation

A definitive method is described for the indirect assay of milligram quantities of D(+)-glucose by coulometric titration. D(+)-Glucose was aerobically oxidized by glucose oxidase in an acetate buffer solution (pH 5.1). Subsequently, the enzymatically formed hydrogen peroxide was titrated coulometrically with electrogenerated hypobromite in sodium bromide-sodium tetraborate medium of pH 8.6, with biamperometric end-point detection. Parameters affecting the enzymatically catalyzed oxidation and coulometric titration were evaluated. The optimized conditions for the oxidation of up to 20 mg of D(+)-glucose include the addition of 4500 U of glucose oxidase and stirring over a 10-min interval at 25 degrees C. Under proposed conditions, the assay values of several commercial D(+)-glucose reagents were somewhat lower than the guaranteed minimum values, with RSDs (n = 5) of 0.071 - 0.106%.