Characterization of kaolin glassy carbon modified electrodes: Preconcentration of 2-chlorophenol

In this paper we describe the use of two kaolin-type aluminosilicate clays, a commercial ceramic-grade kaolin (K) and a natural kaolin from mines in Bolivar State Venezuela (K-Ve), for the preparation of film-based clay-modified glassy carbon electrodes. We examine their behavior during the preconcentration and subsequent anodic oxidation of 2-chlorophenol. Kaolin samples were used as raw materials and modified with cationic surfactant, cetyltrimethylam-monium bromide (CTAB) or nonionic surfactant, octylphenoxypolyethoxyethanol (TX100). The electrode polishing was the key step to produce stable films. 2-Chlorophenol electrooxidation is favored by the presence of the surfactants in the film. The X-ray patterns show that the kaolin K-Ve includes quartz as nonclay mineral, while the kaolin K showed only diffraction peaks characteristic of kaolinite phase. This may be why the TX100/K-Ve/GC electrode adsorbs more 2-CPh than the TX100/K/GC electrode. On the other hand, analysis of the limiting currents obtained from hydrodynamic techniques indicated that the permeability of TX100/kaolin films is greater than that of CTAB/kaolin films. The TX100/K-Ve/GC electrode showed excellent stability. A linear response range from 0.01mgL ^-1 up to 0.1 mg L^-1 with a detection limit of 0.0016 mg L^-1 was observed in the optimized conditions.