Electrochemical Behavior of Amino Acids and their Influence on the Anodic Oxidation of Glucose in Neutral Media

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Abstract
Body fluids contain a large number of amino acids along with glucose. Therefore, the electrochemical behavior of amino acids should be considered in studying the anodic oxidation reaction of glucose for biological applications. Potential-sweep and steady-state measurements with different platinum electrodes under neutral conditions have shown that the oxidation of amino acids is basically possible. However, their presence, especially as a mixture, has a remarkable influence on the glucose oxidation and the anodic reaction is strongly inhibited. With respect to the degree of inhibition, they can be classified into two groups. The inhibiting effect is particularly drastic in the case of basic and unsaturated amino acids as well as the ones containing sulphur because of their strong adsorption at the electrode surface. The glucose currents are inhibited by about 90% under steady-state. In addition to the direct electrochemical inhibition, the following bacterial decomposition of amino acids is probably also reponsible for the drastic effect. However, about 10% of the glucose currents still remain measurable indicating that glucose is detectable at physiological concentrations even under extremly unfavorable conditions. This result is of basic importance in operating a biofuel cell or in measuring glucose concentrations.