ISSN 2738-0971 | eISSN 2738-1013

Branka B. Petković

Faculty of Sciences and Mathematics, University of Priština in Kosovska Mitrovica, KosovskaMitrovica, Serbia

Articles

Open Access Original Scientific Paper

STRUCTURAL AND ELECTROCHEMICAL PROPERTIES OF SYNTHESIZED NANOSTRUCTURED Ca0.9Er0.1MnO3 BY HYDRAZINE NITRITE PROCEDURE

Synthesis, structural, and electrochemical properties of nanostructured powders Ca0.9Er0.1MnO3 with perovskite-type crystal were studied. Nanopowders were prepared by the combustion method using the hydrazine nitrite procedure (HNP), which involves mixing metal nitrate salts (Ca, Mn, Er) in a stoichiometric ratio and varying the quantity of added hydrazine. In this synthetic procedure, the aim is to adjust the amount of hydrazine in order to control the combustion of the reactions, obtain the required amount of fuel energy, but also the amount that will complex the reactants in the mixture. The powders obtained by hydrazine nitrate synthesis were then calcined for 15 minutes at temperatures of 800, 900, and 1000 °C. Characterization of the synthesized and calcined samples was performed using advanced techniques such as X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and electrochemical measurements. The results clearly indicate that the amount of hydrazine added is crucial in preparing the Ca0.9Er0.1MnO3 sample. This highlights the importance of precise hydrazine dosage in optimizing the synthesis process to enhance the material's properties. Further, the electrochemical properties of the obtained perovskite nanopowders were investigated by cyclic voltammetry (CV) and electrochemical spectroscopic impedance (EIS) on perovskite-modified carbon paste electrodes. Electrochemical measurements showed improved electrochemical properties of perovskite-modified carbon paste electrodes compared to bare carbon paste electrode (CPE). The electrode modified with the material synthesized with the smallest amount of hydrazine presented the best results.

Open Access Original Scientific Paper

QUALITY EVALUATION OF WINES FROM KOSOVO AND METOHIJA: POLYPHENOLS CONTENT, ANTIOXIDANT ACTIVITY AND ELEMENTAL COMPOSITION

Wine is a very rich source of polyphenols and essential elements which have multiple biological activities. This study evaluates the total phenolic content (TPC), antioxidant activity (AA) of sixteen wine samples made from different grape varieties in the territory of Kosovo and Metohija, mostly from the area of Orahovac and Velika Hoča. The obtained results, determined by using the Folin-Ciocalteu assay, showed that wines from territory of Kosovo and Metohija are rich in polyphenols, with TPC ranges from 276±16 to 371±46 (white wines) and 1467±32 to 2823±43 mg gallic acid equivalents GAE/L (red wines). The total antioxidant activities, determined by ABTS method, range from 8.7±0.4 to 22.8±0.7 mmol trolox equivalents TE/L for red wines and from 1.3±0.1 to 3.8±0.3 mmol TE/L for white wines. Elemental content of studied wines showed certain difference between wines from nearby regions.