Determination of Fipronil and Fipronil-Sulfone in Surface Waters of the Guandu River Basin by High-Performance Liquid Chromatography with Mass Spectrometry.

Fipronil (FIP) is a broad-spectrum insecticide used in the industrial, residential and agricultural sectors, which presents environmental and human health risks. Studies report its presence in aquatic environments in several countries, but in Brazil reports are scarce. The aim of this work was to evaluate the presence of fipronil and fipronil sulfone in surface waters through a validated analytical method by LC-MS according to INMETRO and USEPA in eight sampling sites in two seasons (summer and autumn, 2020) in Guandu River basin, in the state of Rio de Janeiro. FIP was quantified in the concentration range of 0.132-2.44 μg/L, while FIP-S was detected in most samples. This is the first study on the occurrence of FIP and FIP-S in the Guandu River basin, presenting values high enough to justify the need for monitoring studies in a region of great importance for the city of Rio de Janeiro.