Glucose conductometric biosensor with potassium hexacyanoferrate(III) as an oxidizing agent

A glucose conductometric biosensor has been fabricated by immobilization of glucose oxidase on the sensitive area of thin-film interdigitated electrodes. The properties of the glucose conductometric biosensor with potassium hexacyanoferrate(III) as an electron acceptor have been studied. The use of potassium hexacyanoferrate(III) as an oxidizing agent in the biocatalytic oxidation of glucose increased acidification of the solution inside the enzymatic layer at glucose concentrations above 2 mM. The dynamic range of the biosensor response extended up to 20 mM glucose concentration in the presence of 160 mM potassium hexacyanoferrate(III) in a sample solution. Further increase of the hexacyanoferrate(III) concentration only resulted in a somewhat higher sensitivity of the biosensor. The sigmoidal form of the calibration curve may be explained by the competition between oxygen and potassium hexacyanoferrate(III) as oxidizing agents. It was shown that, at potassium hexacyanoferrate(III) concentrations greater than 40 mM, the measurements must be performed at a low voltage frequency (1-100 Hz), because at higher frequencies (1 kHz and more) no response of the biosensor to glucose was observed. (C) 1998 Elsevier Science B.V. All rights reserved.