Determinação de resíduos de avermectinas em soja, feijão e milho empregando método QuEChERS modificado e UHPLC-MS/MS

Abstract

Soybeans and beans are considered oleaginous plants of great economic importance in Brasil. Maize is a cereal that also generates profitability for the economy, but its use, to a large extent, is as animal feed. In the last years, this crops suffered with infestations of the caterpillar Helicoperva Armigera, being the main problem the resistance of this pest to most pesticides. The indiscriminate use of pesticides and the lack of knowledge and use of good agricultural practices are the main causes of this, as well as undermining food security. Proof of this is the increased presence of pesticides in soil and agricultural crops. The aim of this work was to develop and validate a method based on QuEChERS extraction for the determination of residues of the avermectins: abamectin, emamectin benzoate, eprinomectin, ivermectin and doramectin in soybean, bean and maize samples by ultra-high performance liquid chromatography coupled to tandem mass spectrometry (UHPLC-MS/MS). Avemerctins were selected for the study because of the recent release of emamectin as a pesticide in the three matrices under study. Thus, a method for soybean, bean and maize was developed, where 5 g of sample and 10 mL of ultrapure water were used, as well as a 10 mL mixture of acetonitrile:isopropanol solvents in a ratio of 9:1 (v/v), with subsequent addition of partition salts. In the cleaning step five different sorbents were evaluated: C18 + PSA, Florisil®, silica, Supel™ QuE Z-Sep+ and EMR-Lipid, in their activated and non-activated form. With the clean-up step using EMR-Lipid, limits of detection of 1.2 μg kg-1 for abamectin, doramectin, emamectin benzoate and ivermectin, and of 2.4 μg kg-1 for eprinomectin were achieved. Accuracy and precision evaluated at the levels 4, 8, 20, 40 and 80 μg kg-1 presented satisfactory results. The method was successfully applied in real samples and is a good option for routine analysis