Nanocompósito GO/Y-Fe2O3 para remoção e pré-concentração de agrotóxicos em água superficial e determinação por HPLC-DAD

Abstract

The use of pesticides is fundamental to maintaining high agricultural productivity. However, the indiscriminate use of pesticides can lead to their accumulation in the environment, compromising water sources. As pesticide residues in water are commonly found at trace and ultra-trace levels, the preconcentration is necessary for the quantification of these substances. In preliminary studies on recent trends in the application of magnetic nanomaterials for the adsorption of pollutants from water, presented in the form of a review paper, it was found that magnetic iron oxide nanoparticles combined with graphene oxides were the most used adsorbents for the adsorption of pesticides. Thus, this work presents the synthesis, characterization, and application of oxide graphene-maghemite (GO/-Fe2O3) were carried out for the magnetic dispersive solid-phase microextraction (m-d-μ-SPE) of six pesticides, namely acetamiprid, atrazine, diuron, imidacloprid, thiacloprid, and thiamethoxam in river water samples followed by the determination using high-performance liquid chromatography-diode array detection (HPLC-DAD). The GO/-Fe2O3 nanocomposites were synthesized by the in situ chemical coprecipitation and characterized using Fourier transform-infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy X-ray (EDS). A central composite design was used to optimize the extraction time, sample solution pH, and adsorbent amount. The solvent type and volume for desorption, as well as the effect of the ionic strength for adsorption, were also investigated. The optimum adsorption conditions were obtained at 84 min of extraction time, pH = 5.4, 115 mg of mass, and 1% (w/v) of NaCl, while the desorption solvent selected was 1.0 mL of methanol-acetic acid (9:1, v/v). Adsorption capacities of the adsorbent under optimum conditions were calculated using Langmuir equation (0.9978 ≤ R2 ≤ 0.9997) and were 0.63, 0.82, 3.73, 0.47, 1.51 and 0.23 mg g-1 for acetamiprid, atrazine, diuron, imidacloprid, thiacloprid, and thiamethoxam, respectively. Under optimum conditions, the analytical curve provided good R ≥ 0.9980 over the concentration range applied, low detection (0.1–0.9 μg L-1) and quantification (0.3–1.6 μg L-1) limits, and a good precision with RSD lower than 7.6% (n = 10). The method's accuracy was accessed by recovery tests ranging from 82% to 117% (n = 3, RSDs < 8%). The proposed method was applied for the determination of six pesticides in samples of river water collected in Minas Gerais and Rio de Janeiro states, Brazil. The results demonstrate that the developed method can be promising for extracting pesticides at trace concentrations from environmental water samples.