Amperometric Determination of Glucose in White Grape and in Tablets as Ingredient by Screen-Printed Electrode Modified with Glucose Oxidase and Composite of Platinum and Multiwalled Carbon Nanotubes

Multiwalled carbon nanotubes (MWCNTs) and nanocomposite made from MWCNTs and Pt nanoparticles (Pt-MWCNTs) were used as bulk modifiers of screen-printed carbon electrodes (SPCEs). Cyclic voltammetric and amperometric measurements were performed by the homemade substrate electrodes, the bare SPCE and the modified ones (MWCNT-SPCE and Pt-MWCNT-SPCE), with aim to investigate their applicability for determination of H2O2 in phosphate buffer solution (0.1M; pH7.50) as supporting electrolyte. Pt-MWCNT-SPCE showed improved analytical performances including the significant decrease in overpotential of H2O2 compared to SPCE and MWCNT-SPCE. So, Pt-MWCNT-SPCE served as substrate electrode for design of a simple first-generation biosensor made from glucose oxidase (GOx) and Nafion((R)) forming the GOx/Pt-MWCNT-SPCE for reliable determination of glucose via its enzymatic by-product, the H2O2. The surface morphology characterization by scanning electron microscopy confirmed the presence of immobilized spherical shaped biosensing units at the GOx/Pt-MWCNT-SPCE. In the case of amperometry of glucose, optimal potential for the working electrode was -0.50V vs. SCE, and a satisfactory linearity was obtained in the tested concentration range from 65.8 to 260.6gmL(-1), with estimated LOQ of 35.0gmL(-1). The developed cost-effective amperometric method in combination with GOx/Pt-MWCNT-SPCE was successfully applied for the determination of glucose in selected food samples: white grapes and glucose tablets. The obtained results were in good agreement with those received by the alternatively used commercially available glucometer and by the producer declared value in the case of the tablet sample as well.