All materials and chemicals were purchased commercially and used in the form in which they were received. Manganese sulphate and sodium sulphate for electrolyte preparation, glucose oxidase from Aspergillus niger (100-250 units/mg solid), glutaraldehyde (GA), sodium dihydrogen phosphate dihydrate and sodium hydrogen phosphate dihydrate for preparation of phosphate buffer (PB) (0.1 M, pH 7), glucose monohydrate, hydrogen peroxide (30%) were supplied by Sigma Aldrich. Ultra-pure water (18.2 MΩ cm) from a Sartorius Arium Comfort I system was used to prepare the solutions.