Electrochemical study of antioxidants at a polypyrrole electrode modified by a nickel phthalocyanine complex. Application to their HPLC separation and to their FIA system detections

A polypyrrole electrode modified with a tetrasulfonated nickel(II) phthalocyanine complex (GCE/PPy/NiPcTs) was used as amperometric electrochemical detector in a flow injection system, in order to determine some antioxidants in foods. The lather were separated by HPLC and detected at the modified electrode. Previous investigations carried out in our laboratory employed this electrode and cyclic voltammetry (CV), obtaining excellent results, due to an electrocatalytic effect on the oxidation of certain alimentary antioxidants, such tert-butylhydroquinone (TBHQ), 3-tert-butyl-4-hydroxyanisole (BHA) and propylgallate (PG). In order to obtain good separation, the chromatographic conditions were optimised. The geometry of the flow injection analysis (FIA) circuit and the reproducibility of the results were also optimised and, finally, the linear relationship between the signal and the concentration was verified. The proposed procedure is more precise and accurate than the conventional voltammetry methods. These results offer new analytical possibilities to this type of modified electrodes. The developed methods were applied to the determination of these antioxidants in commercial food.     

In situ spectroscopic study of the oxidation and reduction of Pd(111)

Using a photoemission spectroscometer that operates close to ambient conditions of pressure and temperature we have determined the Pd-O phase diagram and the kinetic parameters of phase transformations. We found that on the (111) surface oxidation proceeds by formation of stable and metastable structures. As the chemical potential of O2 increases chemisorbed oxygen forms followed by a thin surface oxide. Bulk oxidation is a two-step process that starts with the metastable growth of the surface oxide into the bulk, followed by a first-order transformation to PdO.     

Eulerian and Lagrangian Large-Eddy Simulations of an evaporating two-phase flow

Large-Eddy Simulations (LES) of an evaporating two-phase flow in an experimental burner are performed using two different solvers, CDP from CTR-Stanford and AVBP from CERFACS, on the same grid and for the same operating conditions. Results are evaluated by comparison with experimental data. The CDP code uses a Lagrangian particle tracking method (EL) while the code AVBP can be coupled either with a mesoscopic Eulerian approach (EE) or with a Lagrangian method (EL). After a validation of the purely gaseous flow in the burner, liquid-phase dynamics, droplet dispersion and fuel evaporation are qualitatively and quantitatively evaluated for three two-phase flow simulations. They are respectively referred as: CDP-EL, AVBP-EE and AVBP-EL. The results of the three simulations show reasonable agreement with experiments for the two-phase flow case. To cite this article: J.M. Senoner et al., C. R. Mecanique 337 (2009).     

Specific heat of phenolic polymer

The specific heat of a resole-type phenolic polymer has been determined. A secondary transition is noted at 125° C. The thermodynamic Gruneisen parameter is 1.3 and the lattice Gruneisen parameter is 6.3. Interchain specific heat is about 21% of the total.     

Stereochemie vonGrignard-Reaktione mit 2-(N-Methylanikino)-cyclopentanonen

TheGrignard reactions of the 2-anilinocyclopentanones (1 a and1 b) with CH₃MgI and C₆H₅CCMgBr, giving the 2-anilinocyclopentanols2 a, 2 b, and2 c, and the synthesis oftrans-1-methyl-2-(4-chloro-N-methylanilino)-cyclopentanol (4), which was used as a reference compound of known stereochemistry, are described. IR spectroscopic investigations of2 a, 2 b, and2 c as compared with4 lead to the conclusion that2 a, 2 b, and2 c have the structures ofcis-2-(N-methylanilino)-cyclopentanols.