engleski

Evaluation of total antioxidant capacity in bevarages based on laccase immobilized on screen- printed carbon electrode modified with graphene nanoplatelets and gold nanoparticles

A simple and highly sensitive electrochemical biosensor based on laccase immobilized onto a gold nanoparticle/graphene nanoplatelet-modified screen-printed carbon electrode (AuNP/GNPl/SPCE) was developed for the determination of hydroquinone (HQ) and other polyphenolic compounds. The biosensor shows excellent electro- catalytic activity towards oxidation of hydroquinone at a potential of -0.05 V (vs Ag/AgCl, 3M KCl) in phosphate buffer as supporting electrolyte (0.1 M, pH 7.0) using hydrodynamic amperometry. Analytical characteristics uncover that the AuNP/GNPl/SPCE comprises a wide linear range for the dependence of the signal on hydroquinone concentrations from 4 to 120 µM with a detection limit (3σ) of 1.5 µM. The repeatability (5 measurements, 100 µM hydroquinone) is ±2 % and the reproducibility (5 biosensors, 100 µM hydroquinone) is ±3 %. Interference studies of most common compounds with the determination of hydroquinone demonstrated negligible effects. Finally, the biosensor and the proposed analytical method were applied to the determination of total antioxidant capacity (TAOC) in wine, sirup and pharmaceutical drugs based on Trolox (6-hydroxy-2, 5, 7, 8- tetramethylchromane-2-carboxylic acid) and hydroquinone equivalents. The results were evaluated by using their calibration curves which were satisfactory and agreed well with the results obtained by the reference method Trolox Equivalent Antioxidant Capycity assay (TEAC- Assay).

Biosensor ; Antioxidant ; Nanoparticles

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