Avaliação da técnica de extração de SPE e GC-(EI)-MS/MS na análise de agrotóxicos em água de lavoura de arroz irrigado

Abstract

It is known that heavy use of pesticides, especially herbicides and insecticides, associated with the improper management of irrigation water can result in pesticide runoff out the crops to the waters streams, rivers or ponds, since the cultivation of rice is preferably done in areas that have large volumes of water available. Considering the importance of water for nature and human health, the low uncontaminated water resources available today and a large scale production of rice, this study aimed to develop and validate a method for the determination of pesticides in water from irrigated rice crop. Pesticides were extracted from samples of river water using the method of solid phase extraction (SPE). The simultaneous determination of selected pesticides in this study was made by a GC-(EI)-MS/MS. For each analyte, two MRM transitions were optimized, one for quantification and one for confirmation, as predicted by international guidelines and legislations. In the method validation the results were satisfactory for validation requirements, and the analytical curves of r² values are greater than 0.99. The value of the method LOQ for all compounds was established at 0.2 μg L-1. Recoveries for real water samples showed values between 70 and 120% with RSD values lower than 20% for most compounds studied. The results indicate that the proposed method for the analysis of 32 pesticides, including a step of SPE extraction and quantification by GC- (EI)-MS/MS is efficient and selective, allowing the quantification of low levels of concentration appropriate for monitoring these compounds in water. In addition, the validation parameters meet the minimum requirements for the validation of chromatographic methods, which enables the application of the method. Keywords: pesticides; water; GC-(EI)-MS/MS