Evaluation of antioxidant capacity in wine, pharmaceutical formulations and sirup using Laccasse biosenzor

master's thesis

• Title (croatian): Određivanje antioksidativnog kapaciteta u vinu, farmaceutskim proizvodima i sokovima na modificiranom biosenzoru s lakazom
• Author: Ivana Zrinski
• Mentor: Sanja Martinez (mentor)
• Mentor: Kurt Kalcher (komentor)
• Committee member: Sanja Martinez (predsjednik povjerenstva)
• Committee member: Petar Kassal (član povjerenstva)
• Committee member: Kurt Kalcher (član povjerenstva)
• Granter: University of Zagreb; Faculty of Chemical Engineering and Technology; Zagreb
• Defense date and country: 2019-07-09, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Chemical Engineering

Abstract

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 AuNPs/GNPls/SPCE comprises a wide linear range for the dependence of the signal on hydroquinone concentrations from 4 to 130 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 analytical method were applied to the determination of phenolic antioxidant capacity (AOC) in wine and blueberry syrup 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 Capacity assay (TEAC-Assay).

Abstract (croatian)

Za određivanje hidrokinona (HQ) i drugih fenolnih spojeva razvijen je jednostavan i vrlo osjetljiv elektrokemijski biosenzor na bazi lakaze, imobilizirane na nanočestice zlata u grafenskoj tinti modificiranoj sa 2D grafenskim nanopločicama, u obliku sitotiskane ugljične elektrode (AuNP / GNPl / SPCE). Biosenzor pokazuje izvrsnu elektrokatalitičku aktivnost prema oksidaciji hidrokinona pri potencijalu od -0,05 V (vs Ag / AgCl, 3M KCl) u fosfatnom puferu (0,1 M, pH 7,0) kod mjerenja metodom hidrodinamičke amperometrije. Analitička svojstva otkrivaju da AuNPs / GNPls / SPCE širok linearni odziv s povećanjem koncentracije hidrokinona od 4 do 130 μM, s granicom detekcije (3σ) od 1,5 uM. Ponovljivost (5 mjerenja, 100 μM hidrokinona) je ± 2%, a reproducibilnost (5 biosenzora, 100 μM hidrokinona) je ± 3%. Interferencijska ispitivanja za određivanje hidrokinona u prisutnosti različith spojeva pokazala su minimalne smetnje. Konačno, biosenzor i analitička metoda primijenjeni su za određivanje fenolnog antioksidacijskog kapaciteta (AOC) u vinu, sirupu od borovnice i farmaceutskim proizvodima iskazanog preko ekvivalentata standarda Troloxa (6-hidroksi-2,5,7,8-tetrametilkroman-2-karboksilne kiseline) i hidrokinona. Rezultati su ocijenjeni korištenjem kalibracijskih krivulja koje su dobro korelirale s rezultatima dobivenim primjenom referentne metode “Trolox Equivalent Antioxidant Capacity assay” (TEAC-Assay).

• Keywords: antioxidants; graphene nanoplatelets; gold nanoparticle; hydrodynamic amperometry; hydroquinone; screen printed carbon electrode; TEAC Assay
• Keywords (croatian): antioksidansi; grafenske nanopločice; zlatne nanočestice; hidrodinamička amperometrija; hidrokinon; sitotiskana ugljična elektroda; TEAC
• Language: english
• URN:NBN: urn:nbn:hr:149:399309
• Study programme: Title: Applied Chemistry - Graduate study; specializations in: Environmental chemistry and green technologies, Advanced materials and technologies, Applied organic chemistry; Course: Advanced materials and technologies; Study programme type: university; Study level: graduate; Academic / professional title: magistar/magistra primijenjene kemije (magistar/magistra primijenjene kemije)
• Type of resource: Text
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2022-02-27 22:04:43