GLUCOSE CONDUCTOMETRIC BIOSENSOR WITH POTASSIUM HEXACYANOFERRATE(III)AS AN OXIDIZING-AGENT

A glucose conductometric biosensor has been fabricated by immobilizati on of glucose oxidase on the sensitive area of thin-film interdigitate d electrodes. The properties of the glucose conductometric biosensor w ith potassium hexacyanoferrate(III) as an electron acceptor have been studied. The use of potassium hexacyanoferrate(III) as an oxidizing ag ent in the biocatalytic oxidation of glucose increased acidification o f the solution inside the enzymatic layer at glucose concentrations ab ove 2 mM. The dynamic range of the biosensor response extended up to 2 0 mM glucose concentration in the presence of 160 mM potassium hexacya noferrate(III) in a sample solution. Further increase of the hexacyano ferrate(III) concentration only resulted in a somewhat higher sensitiv ity of the biosensor. The sigmoidal form of the calibration curve may be explained by the competition between oxygen and potassium hexacyano ferrate(III) as oxidizing agents. It was shown that, at potassium hexa cyanoferrate(III) concentrations greater than 40 mM, the measurements must be performed at a low voltage frequency (1-100 Hz), because at hi gher frequencies (1 kHz and more) no response of the biosensor to gluc ose was observed. (C) 1998 Elsevier Science B.V. All rights reserved.