Glassy carbon electrode modified with graphene oxide and gold nanoparticles for ascorbic acid detection

Glassy carbon electrodes modified with graphene oxide (GO), gold nanoparticles (AuNP) and methylene blue (MB) were produced by drop casting method for ascorbic acid (AA) determination. Nafion was used as a polymeric immobilizing matrix. The GCE/GO-AuNP-MB-Nafion and GCE/GO-AuNP-Nafion electrodes were characterized by using cyclic voltammetry and electrochemical impedance spectroscopy to investigate electrocatalytic effect, stability and reproductibility. After optimization, the analytical parameters of the modified electrodes were determined by amperometry. The limit of detection for ascorbic acid at GCE/GO-AuNP-Nafion modified electrode was 2.4 µM and the linear domain from 5 to 50 µM. The electrodes showed significant electrocatalytic effect with good stability and reproductibility

Determination of Total Phenolics, Antioxidant Capacity and Antimicrobial Activity of Selected Aromatic Spices

In recent years, it has been acknowledged that many spices not only have properties that make food more pleasant and tastier but they also have important preservative and antioxidant properties. The antioxidant properties of many spices are well known, while their prooxidant properties less so. The aim of this study was to perform a comparative evaluation of three selected spice (garlic, black pepper and red pepper), commercially available in Cluj-Napoca’s market, regarding their content in total phenolic compounds, antioxidant capacity and antimicrobial activity. The antioxidant aspects were evaluated by determination of the total phenolic content by the Folin-Ciocalteau method and by the antioxidant activity using the 1,1-diphenyl-2-picrylhydrazyl reagent (DPPH).The total phenolic content was between 3,38 and 0,925 mg GAE/1g, while the antioxidant capacity ranged between 18,41% and 10,9% from dry spice. .Results  showed that garlic extract has the most effective antioxidant capacity in scavenging DPPH radicals, while black pepper and red pepper were less active. In the present study piperine was evaluated for its antimicrobial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli and Salmonella typhumurium. Spices showed antimicrobial activity against all tested bacteria with zone of inhibition ranged from 8-15,5 mm.</p