Simple and reliable biosensor for determination of glucose in alcoholic beverages

The objective of this work was to determine the glucose in alcoholic beverages using the simple and reliable glucose oxidase (GOx) biosensor. Glucose oxidase was immobilized on the surface of modified graphite electrode in mixed photocurable polymeric membranes of polyacrylamide (PAA)/polyvinylpyrolidone (PVP), taking advantage of both immobilizations; higher activity due to enzyme entrapment (PVP) and longer life of biosensor due to covalent bonding of enzyme (PAA). The surface of graphite electrode was modified with electrodeposited layer of indium (III) and ruthenium (III) hexacyanoferrate films to get faster electron transfer through the surface layer of the modified electrode. Voltammetric and amperometric measurements were performed under batch conditions. The response of biosensor was measured as a function of selected organic solvents (methanol, ethanol and isopropanol) containing phosphate buffer solution (pH=6.5) at −100mV against a reference Hg∣Hg2Cl2∣3M KCl electrode. Addition of 10% of methanol and ethanol increased, while higher volume fractions decreased the biosensor response. On the other hand isopropanol (10%) decomposed the photopolymeric membrane. Therefore, the determination of glucose in alcoholic beverages has been performed in phosphate buffer with 10% of ethanol. The linear range was obtained up to 0.8mM (R2=0.9925) for mixed solvents, as well as phosphate buffer (R2=0.9996). The simple, fast and easy preparation of the biosensor, high activity and long life, if glucose was immobilized in mixed polymeric photocurable membrane, and reasonably accurate glucose determination, make the proposed procedure appropriate for quality control of the alcoholic beverages in mixed solvents.