Current oscillations during the anodic dissolution of copper in trifluoroacetic acid

A phenomenon of current oscillators was characterized crosswise active-passive potential region during the electrodissolution of copper electrode in trifluoroacetic acid (TFA). The current density-potential curves show two transition points. A potential region of current oscillations was found as a part of limiting current region. The Cu vertical bar TFA electrochemical oscillator was found to displaying rich dynamical response on varying the temperature and the applied potential. The Cu vertical bar TFA system display current oscillation behaviour from the mono-periodic to the mixed-mode (relaxation type). Changes of the electrode surface structure and morphology were investigated by X-ray diffraction spectroscopy, atomic forced microscopy and optical microscopy

Antioxidant Activity of Wines Determined by a Polarographic Assay Based on Hydrogen Peroxide Scavenge

Antioxidant (AO) activity of various red and white wines of different origin as well as some individual phenolic compounds present in wine has been assessed using a polarographic assay. Direct current polarography has been used to survey hydrogen peroxide scavenge (HPS) upon gradual addition of tested samples. Results expressed as reciprocal value of wine volume required for 50% decrease of anodic limiting current of hydrogen peroxide have been validated through correlation with Folin Ciocalteau and DPPH assays. All wines exhibit HPS activity analogous with total phenolic content and DPPH scavenge. Reliability and accuracy, low cost, and rapid and direct experimental procedure open a wide area for application of this assay, making it a good alternative to standard, widely accepted AO assays

Application of a Novel Antioxidative Assay in Beer Analysis and Brewing Process Monitoring

A novel antioxidative assay based on direct current polarography has been developed. Quantification of antioxidative (AO) activity has been based on a decrease of hydrogen peroxide anodic current in the presence of antioxidants. An efficient experimental procedure, without any special pretreatment of analyzed samples, has been applied. Antioxidative activity of different kinds of commercial beers (dark, blond, and alcohol-free), some small-scale made special beers with medicinal herbs and Mushroom extracts, extracts themselves, as well as individual phenolic components present in beer has been measured. In addition, changes of AO activity during the full-scale industrial process of beer production have been monitored. A strong correlation between results obtained and total phenolics content has been observed. The assay can be recommended for application in brewing industry, either to survey 1 process with the aim to optimize relevant technological factors or to analyze quality of final product

Antioxidant activity of propolis extracts from Serbia: A polarographic approach

Antioxidant activity (AO) of commercial propolis extracts (PEs), available on Serbian market, was determined by direct current (DC) polarography. Polarographic anodic current of 5.0 mmol L-1 alkaline solution of H2O2 was recorded at potentials of mercury dissolution. Decrease of the current was plotted against the volume of gradually added PEs. The volume of PE causing 20% current decrease was determined from the linear part of the plot. Antioxidant activity was expressed in H2O2 equivalent (HPEq), representing the volume of PE that corresponds to 1.0 mmol L-1 H2O2 decrease. Resulting HPEq ranged between 1.71 +/- 0.11 and 8.00 +/- 0.18 mu L. Range of 1,1-dipheny1-2-picryl hydrazyl (DPPH) radical scavenging activity was from 0.093 +/- 0.004% to 0.346 +/- 0.006%. Total phenolic content (TCP) of PE with superior AO activity was 5.31 +/- 0.05%g GAE, while the extract with the lowest activity contained 1.45 +/- 0.02%g GAE. Antioxidant activity, determined by polarographic method, was correlated with DPPH scavenging activity (R-2 = 0.991) and TCP (R-2 = 0.985). Validity of obtained results was further confirmed using ANOVA and post hoc Tukey HSD test