Desenvolvimento de metodologia eletroanalítica para a detecção de imidacloprido

Abstract

In this work, an electroanalytical methodology was developed using a solid silver electrode with silver amalgam combined with the technique of square wave voltammetry for the identification and quantification of imidacloprid. The results indicated that imidacloprid undergoes a reduction reaction with characteristics of an irreversible process and with slow electrodic kinetics. A Britton-Robinson buffer solution was employed as the supporting electrolyte, with pH values ranging from 6 to 12, and the best voltammetric signal was obtained at pH 8.0. Pre-concentration steps were also evaluated with optimization of the pre-concentration potentials (EPC) and pre-concentration time (tPC), which were optimized at the value of -0.5 V and 15 s, respectively. A linear range of concentration was obtained in the range of 2.3x10-6 to 1.8x10-5 mol/L using the optimized parameters of: frequency of potential pulse application (f = 40 s-1 ), amplitude of potential pulse application (a = 50 mV) and potential sweep increment (ΔEs = -2mV). Detection and quantification limit values were calculated, resulting respectively in 1.62x10-6 and 5.41x10-6 mol/L, indicating that the proposed methodology showed good sensitivity outperforming many other methodologies with the same focus. The method was accurate, presenting low coefficients of variation for the repeatability and reproducibility tests, with values equal to 2.01% and 4.22%, respectively. The recovery rate found was 123%, a relatively high value, probably due to the adsorptive effect of the irreversible redox reaction of imidacloprid, which was a factor that contributed to the changes in the analytical signal. Thus, the proposed methodology proved to be sensitive, selective and accurate for the determination of imidacloprid. In addition, the methodology presents other advantages such as low cost, good reproducibility, and environmental feasibility. In the future the proposed methodology will be applied for the detection of imidacloprid in milk and honey samples.