Cobalt oxide electrodeposition on various electrode substrates from alkaline medium containing Co-gluconate complexes: a comparative voltammetric study

Abstract: A study regarding the electrodeposition of Co oxides from alkaline medium containing 12 mM gluconate ligand and 12 mM Co2+ on glassy carbon, Au, Pt, Ni, Ti and ITO electrode substrate was carried out through cyclic voltammetry technique. Films of cobalt oxides were deposited either anodically by voltage cycling (100 mV s(-1)) between -0.3 and 0.6 V (SCE) or by potentiostatic conditions at potential comprised between 0.2 and 0.6 V for a fixed time of deposition. Analysis of the voltammetric experimental data clearly showed that the rate of cobalt oxide electrodeposition process decreases in the order Au > Pt > GC, Ni > Ti, ITO and the massive cobalt electrodeposition does not proceed to an appreciable extent until potentials of 0.3-0.4 V (SCE) is reached. The effect of the scan rate on the peak potential, peak current, an

CHROMATOGRAPHIC SEPARATIONS AND LIQUID PHASE EXTRACTION/CONCENTRATION OF SOME POLYPHENOLIC COMPOUNDS: A COMPARISON BETWEEN REVERSE PHASE AND CATION-EXCHANGE CHROMATOGRAPHY.

Chromatographic performance based on the use of a C-18 reverse phase and a LC-SCX cation-exchange column associated with UV absorption at 280 nm is optimized and compared for the simultaneous determination of resveratrol and other polyphenolic compounds with the aim to establish the best experimental conditions for the trace analysis of these substances. Under the optimized chromatographic conditions using a gradient acid mobile phase and acetonitrile as a modifier solvent, the elution of all injected compounds was completed in about 30 min of analysis and the detection limits (LOD) ranged between 20 nM and 120 nM. The regression analysis for most of the analyzed compounds shows linear ranges spanning over five orders of magnitude with correlation coefficients always >= 0.98. A liquid-liquid extraction procedure was optimized using three different extracting solvents such as methyl ethyl ketone, diethyl ether, and dichloromethane. The hydrophilic/hydrophobic character of the water/organic solvent was modulated by addition of NaCl salt. In order to ascertain the analytical potentialities of the investigated method, and in particular the performance of the extraction procedure, a wide variety of selected red wines were analysed. The average recoveries ranged between 73% and 103% for the analysed molecules, indicating both the practical absence of interfering peaks on the chromatographic separation and an appreciable capacity of extraction of polyphenolic acids from the wine matrices