Otimização do método de extração sólido-líquido com partição à baixa temperatura de resíduos de agrotóxicos em polpa de pequi

Abstract

The high load of pesticides employed in grain and sugarcane crops in the Brazilian Cerrado, especially through leaf spraying, has put at risk of contamination a wide range of territorial extension. Among these, native fruit trees from the Cerrado, which have been recently discovered by Brazilians, may be receiving pesticide residues indirectly. Therefore, the monitoring of pesticides in fruits most consumed by local people is necessary to ensure food security. This work aimed to develop a method to determine residues of six pesticides in the Pequi pulp, the most identity fruit of the Brazilian Cerrado region. For this, the work describes the development and optimization of solid-liquid extraction with low-temperature partitioning (SLE-LTP) residues of the pesticide carboxin, carbendazim, chlorpyrifos, diuron, terbuthylazine and thiabendazole of Pequi pulp, with analysis of extracts by high-performance liquid chromatography with a diode array detector (UV-VIS). The optimization of the SLE-LTP method was performed by experimental design, and eight factors at different levels that affect the pesticide recovery from Pequi pulp were evaluated. The optimized factors were extractor solvent - ethyl acetate; solvent volume - 7.2 mL; sample mass - 0.5000 g; type of agitation - Vortex; water volume - 3.4 mL; freezing time - 3 h; contact time - 15 min; and absence of centrifugation in the partitioning step. The optimized conditions resulted in the extraction of pesticides from Pequi pulp in the range of 71.0-103.7 %. The method of analysis of pesticides was relatively fast, with a total time of 12 min of analysis. The validation of the method was performed from the evaluation of some analytical parameters of the method. Validation showed a good linearity of response of the method over a wide range of pesticide concentrations. The method presented quantification limits, 0.008 to 0.500 mg L-1, below other methods developed to determine the pesticides studied in food matrices. The effectiveness of the SLE-LTP method for extracting pesticide residues from Pequi pulp was confirmed by the high recovery rates of pesticides and the clear and interference-free extract (low matrix effect) obtained in the work. In this way, it was possible to develop and optimize the SLE-LTP method for the extraction of pesticide residues in Pequi pulp, providing an analytical tool for the monitoring of pesticide residues in this fruit, which is not currently available in the literature.