Électroanalyse de la carbendazime et du glyphosate sur des électrodes modifiées par des smectites organophiles

Abstract

Clay minerals are materials that are particularly solicited for the removal and the detection of environmental pollutants. In this work, a Cameroonian smectitic clay whether or not pretreated with acid was modified by grafting of octyltriethoxysilane (OTES), in order to increase its organophilic character. The influence of the nature of the synthesis solvent (toluene or ethylene glycol) on the organization of the grafted moities was examined, the objective being to obtain an adequate material for the electroanalysis of organic compounds. The materials obtained were characterized by X-ray diffractometry, nuclear carbon 13 magnetic resonance (13C NMR), Fourier transformer Infrared (FTIR), measurement of specific surface areas by nitrogen adsorption. The results obtained showed that acid treatment induces the formation of silanol groups in the intermellar (or interlayer) space available for OTES grafting. In addition, ethylene glycol appears to be the ideal solvent to limit the anarchic polymerization of silane during grafting, and occlusion of the pores of the material. The electrochemical characterization of the materials by [Ru(NH3)6]3+ ions confirms the good porosity of the material resulting from the functionalization of the natural clay mineral in ethylene glycol. The materials were later applied to the quantitative electroanalysis of carbendazim and glyphosate, two widely used pesticides with proven toxicity. The carbon paste electrode was chosen for its simplicity of preparation and especially for the easy renewal of its active surface. Overall, the best results are obtained with electrodes modified by the functionalized clay mineral. In the case of carbendazim, after optimization of the detection parameters on the most efficient sensor, a detection limit (DL) of 0.03 μM, determined for a signal/noise ratio of 3 was obtained. This sensor remains sufficiently effective in river water (DL 0.2 μM). Despite the lower performance of the optimized sensor for the detection of glyphosate (DL of 1.22 μM), it can be used to monitor soil contamination with this pesticide. These interesting results confirmed that by controlling the grafting of organophilic compounds on a smectite, it is possible to obtain efficient electrode materials for the electrochemical detection of organic compounds.