Nanopartículas de Fe3O4@quitosana como Sensor Eletroquímico de Bendiocarbe

Bendiocarb (1,3-benzodioxol-4-ol, 2,2-dimethyl-, methylcarbamate, BND) is used in vector control of Malaria and Chagas diseases, classified as class I, being a harmful carbamate insecticide, since it is able to inhibit the activity of the enzyme acetylcholinesterase, which acts as a neurotransmitter. In this perspective, an electrochemical sensor was developed for detection and quantification of BND based on the modification of the glassy carbon electrode (GCE) by magnetic iron oxide nanoparticles and chitosan (Fe3O4@CH). This nanocomposite was synthesized according to methodology described in the literature1 . The stock solution of 1.0 × 10−3 mol L−1 BND was prepared by dissolving an appropriate mass in ethanol. Square-wave voltammograms for BND on Fe3O4@CH/GCE were recorded in order to evaluate the BND electrochemical response and the results showed an irreversible oxidation peak on 1.34 V (vs Ag/AgCl/Cl− ) in BR buffer pH 3 (at optimized conditions) containing 2.91 × 10−5 mol L−1 BND with f = 100 s−1 , a = 50 mV and ΔEs = 2 mV. For the electroanalytical determination of BND, a study was made to verify the influence of the values of accumulation time and potential of the electroactive species on the values of peak currents for BND oxidation. To this end, the accumulation potential was varied from 0.60 to 1.25 V for periods of time ranging from 5 to 120 s, and the responses were evaluated by the square-wave voltammetry (SWV). Thus, the highest peak currents and analytical reproducibility for BND were attained with 1.15 V as accumulation potential for 60 s. The optimized parameters in BR buffer pH 3.0 were f = 80 s-1 , a = 60 mV and ΔEs = 1 mV. A linear correlation between values of peak currents and BND concentration [BND] was observed for [BND] ranging from 4.97 × 10−6 mol L−1 to 3.01 × 10−5 mol L−1 , following Ip/A = −2.14 × 10−6 + 0.06 [BND/mol L−1 ] with r = 0.9937. The values of the detection and quantification limits obtained by the proposed procedure were calculated as recommended by IUPAC, being equal to 2.09 × 10−6 mol L−1 and 6.97 × 10−6 mol L−1 , respectively. The relative standard deviation (RSD) values for reproducibility (n = 5) and repeatability (n = 7) experiments were 2.76% and 1.83%, respectively. The recovery percentages were calculated by adding BND in five levels of fortification (from 9.90 × 10−6 to 2.91 × 10−5 mol L−1 ) resulting in 81.26% (RSD 8.01%), 79.63% (RSD 2.32%) and 79.33% (RSD 6.44%) for BR buffer pH 3.0, Gavião raw natural waters and Acarape do Meio raw natural waters, respectively. In conclusion, the proposed electroanalytical methodology was successfully applied suggesting that modified electrode has potential to BND determination in complex samples.