Otimização de um eletrodo de carbono vítreo modificado com nanotubos de carbono para detecção voltamétrica do fungicida carbendazim.

Abstract

For many years the mercury electrode has been widely used as working electrode in electrochemical analysis. However, new electrode materials, such as the glassy carbon, carbon paste, platinum, gold, among others, are excellent alternatives to the mercury electrode because of the ease of construction, wide potential window and low toxicity. Recently, new materials as carbon nanotubes have been used, so promising, at the construction of chemically modified electrodes, that coupled electroanalytical techniques improve the determination of pesticides residues in food and environmental samples, presenting high sensitivity and selectivity. Accordingly, this work proposes the construction and optimization of a glassy carbon electrode chemically modified with carbon nanotubes multiwalled (GCE-MWCNTM). Square wave voltammograms of the fungicide carbendazim (MBC) were recorded and the results showed the feasibility of building a GCE-MWCNTM (1.0 mg L-1) dispersed in water using acetate buffer ( pH 4.7) and sulfuric acid (pH 1.0) as supporting electrolyte. The GCE-MWCNTM was characterized electrochemically by oxidation of the MBC, using cyclic voltammetry and square wave voltammetry with pre-concentration. This characteristic occurred because of the ability to pre-concentration MBC on the nanotubes and the excellent voltammetric response of the material pre-concentrate, with no evidence of memory effect, combined with easy preparation of the electrode. The accuracy of the modified electrode was assessed by tests of repeatability and reproducibility, which showed a relative standard deviation of about 7.8 and 8.23%, respectively, below the limit of 20% for analysis of pesticide residues, which allows to use it for develop a voltammetric method for determination of MBC residues in food and environmental samples.