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Based on graphene nanoplatelets capability to build block composites, as well as well-known electrochemical characteristic of the manganese oxide materials, in the present research, a nanocomposite, formed from graphene nanoplatelets (GNP) and manganese(IV)-oxide (MnO2) nanoparticles, has been proposed as a novel and convenient support for enzyme immobilization. Performance of screen printed carbon electrodes (SPCEs) was significantly improved after their modification with GNP@MnO2 (SPCE/GNP@MnO2). The polyphenolic index biosensor was prepared by applying the drop coating technique using laccase and Nafion®. Developed biosensor shows a fast and reliable amperometric response toward caffeic acid, as a model compound, at operating potential of +0.40 V (vs Ag/AgCl), with a wide linear range and detection limit of 1.9 μmol l−1. Developed procedure was successfully applied for the determination of polyphenolic indexes in wine samples. Recovery tests indicate excellent accuracy and precision of the method, concluding that the biosensor can offer a fast, accurate, reliable and precise determination of the polyphenolic index. More importantly, our results suggest a great potential for the application in real samples.

A nanocomposite formed from graphene nanoplatelets (GNP) and manganese oxide (MnO2) nanoparticles (GNP/MnO2) was proposed as a novel and suitable support for enzyme immobilisation. The performances of screen-printed carbon electrodes (SPCEs) was highly improved after modification with GNP/MnO2 (SPCE/GNP/MnO2). The polyphenol index biosensor was prepared by surface modification of SPCE/GNP/MnO2 with drop coating of the laccase (from Trametes Versicolor) and Nafion®. All electrochemical measurements were carried out in acetate buffer, pH=4.60. The developed laccase biosensor shows fast and reliable amperometric response toward caffeic acid, as model compound, at operating potential of +0.40 V (vs. Ag/AgCl), with a linear range from 5 μmol L-1 to 2.75 mmol L-1 (r2 = 0.9997), with detection limit of 2.38 μmol L-1. Moreover, effects of possible interfering compounds were investigated. The developed procedure was successfully applied for the determination of total polyphenol content in red and white wine samples. In order to validate the proposed method, the polyphenol content in wine samples, under optimized parameters, was determined using a glassy carbon electrode. Recovery tests (95.7-97.5%) shows satisfactory accuracy and precision of the developed method, concluding that proposed construction of biosensor can offer fast, stable and reproducible determination of the polyphenol index.

FLWNA, info:eu-repo/semantics/published

FLWNA, info:eu-repo/semantics/published