Validação de método multirresídual e monitoramento de resíduos de agrotóxicos por GC-μECD em méis do estado do Rio Grande do Sul

Abstract

Due to the complexity of matrices such as honey and the low concentrations of pesticides, there is a great need for the development of efficient and reliable analytical methods for the identification and quantification of these residues. The greatest advantage of a multi-residual method is the possibility of determining a variety of pesticides in the same chromatographic analysis. Thus, this work carried out the validation of the multi-residual method for the determination of pesticides in honey by GC-μECD. The parameters of matrix effect and linearity of the analytical curve were evaluated in terms of coefficient of determination (r2) and residues. The determination of the limits of quantification and detection, accuracy and precision was performed through the fortification/recovery studies, in the following concentrations: 5, 10, 20 and 50 μg kg-1 in seven replicates each (n=7). For the determination of pesticides 10 mL of ultrapure water was added to 10 g of honey followed by stirring. Then 10 ml of acetonitrile 1% acetic acid (v/v) were added and stirred. To the partition step was added 4 g of MgSO4 and 1 g of sodium acetate followed by stirring and centrifugation. 2 mL was transferred into the tube containing 300 mg of MgSO4 and 50 mg of PSA to perform the purification step followed by stirring and centrifugation. Finally 1.2 mL of extract was evaporated and resuspended in 1.2 mL of isoctane/toluene (9:1, v/v). 990 μL of the extract in vial and 10 μL of I.I.S. Most pesticides presented linearity of 2.5 to 200 μg L-1. Regarding to limits of detection and quantification, 78.9% of the pesticides studied presented LOD of 2.5 μg kg-1, 57.9% of pesticides presented LOQ of 5 μg kg-1, 36.8% LOQ of 10 μg kg- 1 and 5.3% LOQ of 20 μg kg-1. The results obtained for the validation were considered satisfactory according to the SANTE 2017. The recoveries between 70 and 120% and RSD <20% were obtained for all pesticides. The matrix effect had no great influence on the results in the determination of pesticides by GC-μECD. Honey samples from different regions of Rio Grande Sul were analyzed and none of them presented concentration values higher than LOQ.