Desenvolvimento e aplicação de um eletrodo modificado com nanotubos de carbono na determinação voltamétrica do pesticida carbendazim em suco de laranja

Abstract

This work describes the development and application of an electrode modified with films of multi-walled carbon nanotubes (MWNTC) and chitosan for quantification of the fungicide carbendazim (CBZ) in orange juice, using a glassy carbon electrode (ECV) as electrode base. To make the modified electrode, 5 mg of chitosan and 2 mg of MWNTCs were added to 1 mL of 1% acetic acid solution (v/v) pH 5.0, taken to ultrasound and applied to the surface of the ECV. In the analytical application of the electrode for the determination of carbendazim, an irreversible oxidation peak was observed at +0.77 V, vs. Ag/AgCl, in 0.1 mol L-1 phosphate buffer (pH 7.0). The instrumental parameters of differential pulse voltammetry were optimized, and the best response in terms of sensitivity and selectivity was obtained by applying pulse amplitude (△Ep) of 100 mV, potential increment (Es) of 10 mV and pulse time ( tp) of 0.2s. The analytical curve was obtained in the concentration range from 1.0 to 25.0 mg L-1 (R2 = 0.99301), in 0.1 mol L-1 phosphate buffer solution, with detection limits (LD) of 0.230 mgL-1, and limits of quantification (LQ) of 0.698 mg L -1 . For the analysis of the real sample of CBZ in diluted commercial orange juice, the linear concentration range from 1.0 to 25 mg L-1 (R2 = 0.98945) was obtained, with higher detection and quantification limits reached, of 0.763 mg L1 and 2.310 mg L-1, respectively. The proposed method also provided repeatability and reproducibility measures with a relative standard deviation below 6%.