Electrocatalytic oxidation of phenolic acids at the surface of TiO2 nanoparticle modified carbon paste electrode

Abstract

Cilj ovog rada bio je utvrditi utjecaj umješavanja TiO2 nanočestica u elektrodu od grafitne paste na cikličke voltamograme fenolnih kiselina, odnosno njihovih derivata topivih i netopivih u vodi. Također cilj je bio osmisliti strategiju primjene nanočesticama modificirane elektrode u svrhu istraživanja antioksidativnog djelovanja fenolnih kiselina usporedbom sa antioksidativnim standardima. Kao vodotopivi antioksidativni standardi odabrane su mokraćna i askorbinska kiselina te je istražen njihov voltametrijski odziv na elektrodi od grafitne paste pri različitim koncentracijama i brzinama polarizacije, vremenima stajanja otopine na zraku. Istraživanja koja su uključivala galnu kiselinu, provedena su na istoj elektrodi, bez i sa 10 % TiO2 nanočestica umiješanih u grafitnu pastu. Kumarin i 7-hidroksi kumarin ispitivani su kao standardi netopivi u vodi, a kao primjeri u vodi netopivih antioksidansa, ispitivani su različiti heterociklički derivati kumarina. Netopivi antioksidansi umiješavani su u elektrodu bez i sa 10 % nanočestica TiO2. Na temelju dobivenih rezultata može se zaključiti o antioksidativnim svojstvima ispitivanih spojeva, njihovoj stabilnosti i elektrokatalitičkom utjecaju dodatka TiO2 nanočestica u grafitnu pastu na oksidaciju ispitivanih spojeva. Uočen je izrazit elektrokatalitički efekt kod spojeva otopljenih u vodi, a kod spojeva umiješanih u elektrodu, TiO2 nanočestice smanjuju strujni odziv.The aim of this work was to establish the impact of mixing in TiO2 nanoparticles in carbon paste electrode on cyclic voltammograms of phenolic acids, with reference to their derivatives soluble and indissoluble in water. Moreover, the aim was to invent the strategy on the application of nanoparticles modified electrode for the purpose of researching antioxidant effect of phenolic acids compared to the antioxidant standards. There were chosen ascorbic and uric acid as water-soluble antioxidant standards and there was researched their voltammetric response on carbon paste electrode at different concentrations, polarization rates and solution standing time on the air. Researches that have included gallic acid are conducted on the same electrode, without and with 10 % TiO2 nanoparticles mixed in carbon paste. Coumarin and 7-hydroxycoumarin were tested as water-indissoluble standards, and as water-indissoluble antioxidants there were tested different heterocyclic derivatives of coumarin. Water-indissoluble antioxidants were mixed in electrode without and with 10 % TiO2 nanoparticles. Based on the given results, it could be concluded about antioxidant properties of tested compounds, their stability and electrocatalytic influence of TiO2 nanoparticles addition in carbon paste on oxidation of tested compounds. There was observed distinct electrocatalytic effect on water-soluble compounds, and on compounds mixed in electrode TiO2 nanoparticles decreased current response