Development and optimization of electrochemical method for determination of antioxidant capacity : bachelor thesis

Abstract

Poznato je kako elektrode izrađene od ugljikovih materijala (grafita, staklastog ugljika, ugljikove paste ili grafena) zbog niskog omskog otpora mogu značajno poboljšati elektroanalitička svojstva osjetnih slojeva i pružaju različite mogućnosti modifikacija koje se često koriste za razvoj visoko osjetljivih senzora za istraživanje elektrokemijskih svojstava i otkrivanje raznih spojeva. Prvi cilj ovog rada bio je razviti jednostavnu elektrokemijsku metodu za određivanje vitamina C (VitC) na posebno konstruiranoj mikroelektrodi od lista pirolitičkog grafita (PGS – Pyrolytic Graphite Sheet). Ciklička voltametrija korištena je za karakterizaciju mikroelektrode i pravokutnovalna voltametrija za elektroanalitičke svrhe. Utvrđen je postupak za kvantificiranje VitC –a u realnom uzorku. VitC pokazuje jednu kvazireverzibilnu reakciju koja uključuje prijenos dva elektrona, dok potencijal oksidacije ovisi o koncentraciji analita. Pravokutnovalna voltametrija (SWV) optimizirana je i provedeno je analitičko određivanje u području potencijala od –0,30 do 0,80 V. Dobiveni rezultati pokazuju linearni odziv PGS elektrode u širokom području koncentracija. Drugi cilj bio je utvrditi učinak dodavanja različite vrste „zelenog“ biootpada na rast biljaka, sadržaj VitC –a i antioksidacijsku aktivnost u rikoli (Eruca sativa L) uporabom PGS elektrode. Dobiveni rezultati uspoređeni su sa standardiziranim metodama. Nakon tri tjedna uzgoja uočene su male razlike u rastu i velike razlike u određenim nutritivnim karakteristikama. Dodavanje ljuske kikirikija doprinosi prozračivanju tla, a primijećen je i najbrži razvoj zdrave i zelene Eruca sativa. Dodatak crne kave čini tlo blago alkalnim i rezultira značajnim povećanjem sadržaja VitC –a i antioksidacijske aktivnosti.It is known that electrodes made of carbon materials (graphite, glassy carbon, carbon paste or graphene) due to low ohmic resistance can significantly improve the electroanalytical properties of sensitive layers and provide a variety of modification options that are often used to develop highly sensitive sensors for investigation of electrochemical properties and give opportunity for detection of various compounds. The first goal of this work was to develop a simple electrochemical method for the determination of vitamin C (VitC) on a specially constructed microelectrode made from the Pyrolytic Graphite Sheet (PGS). Cyclic voltammetry was used to characterize the microelectrode and square wave voltammetry for electroanalytical purposes. A procedure for quantifying VitC in a real sample was established. VitC shows a single quasi–reversible reaction involving the transfer of two electrons, while the oxidation potential depends on the analyte concentration. SWV was optimized and analytical determination was performed in the potential range from –0.30 to 0.80 V. The obtained results show a linear response of the PGS electrode in a wide range of concentrations. The second goal was to determine the effect of adding different types of "green" biowaste on plant growth, VitC content and antioxidant activity in arugula (Eruca sativa L) using PGS electrode. The obtained results were compared with standardized methods. After three weeks of cultivation, small differences in growth and large differences in certain nutritional characteristics were observed. The addition of peanut shell contributes to soil aeration, and the fastest development of healthy and green Eruca sativa has been observed. The addition of black coffee makes the soil slightly alkaline and results in a significant increase in VitC content and antioxidant activity