Ana Valeria Juarez

Electrochemical Study of a Dendritic Family at the Water/ 1,2-Dichloroethane Interface

The transfer of six dendritric molecules, DMs, across the water/1,2-dichloroethane interface was investigated using cyclic voltammetry. From the variation of peak potential with pH, two different mechanisms of transfer were postulated depending on the nature of the molecules. Voltammetric parameters were employed to evaluate the hydrophilic/hydrophobic character and calculate the acid dissociation constant of these molecules. The results were explained taking into account the nature and multiplicity of functional surface groups.

Electrochemical behaviour of cationic polyelectrolytes at a polarized liquid/liquid interface

The behaviours of several cationic polyelectrolytes (chitosan; polyquaternium-4; diethylaminoethyl dextran; polyquaternium-10, and aminoacrylmethacrylate copolymer, Eudragit® E100) at a polarised liquid/liquid interface are analysed and compared in the present paper. Based on the analysis of the voltammetric results, it was possible to determine some of the relationships between polymer structure and the tendency to adsorb at the interface. It was also possible to determine the substitution degree of a polymer comprising a chitosan main chain modified with glycidyltrimethylammonium chloride, and the values obtained are in agreement with those calculated using other methodologies. Finally, we report a comparative study concerning the effect of cationic (chitosan) and anionic (dextran sulphate) polyelectrolytes on the compactness of a phospholipid film.

An Electrochemical Approach to Quantitative Analysis of Herbicides and to the Study of Their Interactions with Soils Components

R2 Fig. 1. Chemical structure of s-triazine core, substituent in R1 : Cl, SCH3 or OCH3; R2 and R3: hydrocarbons chains. These herbicides have been extensively applied to pre and post-emergence weed control. Many studies were focused on ecological and health hazards of these compounds and their toxic effects are very well known. For this reason, the use of some triazine pesticides has been banned in some countries or their permitted levels in drinking water is very low, so that analytical procedures for quantitative determination of several triazines, as well as their degradation products, at low levels are often requested. In this sense, several analytical techniques have been developed, like HPLC (Katsumata et al., 2006), CG-MS, capillary electrophoresis (Frias et al., 2004), solid-phase micro-extraction coupling with GC, LC, ion mobility spectrometry (Garcia Galan et al., 2010; Mohammadi et al., 2009; Sanchez Ortega et al., 2009; Quintana et al., 2001) and with HPLC (Zhou et al.,