Desenvolvimento e validação de método analítico multiresíduo para pesticidas em extrato de soja utilizando microextração líquido-líquido dispersiva e cromatografia a gás acoplada a espectrometria de massas (CG-EM)

Abstract

Resumo em inglês Soy is a grain that besides having several functional benefits originates products and by- products very used in the food industry. In human food, soybeans stand out as a substitute alternative for other foods and because it is a food with a high protein content and low cost. In view of the increased use of soy and its derivatives in human food, it is important to evaluate these foods for contamination by pesticide residues. In this context, this study aimed to develop a simple method to extract the pesticides from the soybean extract matrix using liquid-liquid dispersive microextraction (DLLME) and to validate the method by gas chromatography coupled to mass spectrometry (GC-MS) for quantitative determination of the same. Initially, 5.0 mL of soybean extract, sodium chloride (NaCl) and acetonitrile were added as a salting-out agent and extraction solvent, respectively. After manual stirring, the mixture was centrifuged and, in the presence of sodium chloride, a two-phase system was formed: upper phase, acetonitrile containing the pesticide mixture and lower phase, aqueous phase containing soluble compounds and precipitated proteins. After the extraction of pesticides from the soybean extract, a portion of supernatant phase (acetonitrile) was removed, mixed with carbon tetrachloride and rapidly injected via syringe into 5.0 mL of ultrapurified water. In this process, the pesticides were extracted in small drops of carbon tetrachloride, used as the extraction solvent of the process. After centrifugation, the fine carbon tetrachloride droplets were settled on the bottom of the conical test tube. Subsequently, CG-MS were used for the separation and determination of analytes in the sedimented phase. Important parameters for optimization of the DLLME technique were evaluated as the type of solvent for extraction, quantity of salt and volume of extraction solvent, which affect the extraction efficiency. The validation results were satisfactory considering that the optimized method presented a limit of detection (LOD) and quantification (LOQ) of 0.170 μg/mL and 0.500 μg/mL respectively, linearity in the range of 0.50 to 5.0 μg /mL, recoveries in the range of 47 and 115%, with RSD of less than 20% for fortification levels between 1.0 and 3.0 μg /mL, besides not being influenced by the matrix, proving to be selective, precise and extremely simple, fast and low cost.