Development and validation of a solid–liquid extraction with low-temperature partitioning method for the determination of fipronil in turtle eggshell

Abstract

The intense use of fipronil in sugarcane crops in Brazil in regions close to the spawning areas of freshwater turtles may pose a considerable threat to the reproduction of these organisms. Therefore, the development and validation of a method to quantify the fipronil contamination in turtle eggshells is pressing and constitutes the main goal of the present study. The proposed method was based on solid–liquid extraction with low-temperature partitioning, reducing its scale due to the limited availability of turtle eggshell samples. The fipronil extraction from eggshell samples was optimized using a statistical design based on the Doehlert Matrix. Eggshell mass, the volume of extraction solvent, and the freezing time were the optimized method parameters, yielding fipronil recoveries close to 100% without a clean-up step. Furthermore, the optimized method was linear, robust, precise, and accurate in the fipronil concentration range of 8.4–1,818.0 µg kg−1. The limit of quantification for fipronil was 8.37 µg kg−1, about 2.5 times lower than the maximum residual limit for fipronil in eggs. Residues of fipronil were detected and quantified successfully in amazon-turtle eggshell samples using the proposed method. In conclusion, the one-step SLE-LTP method was mini-scaled for the first time and presented a strong potential for monitoring fipronil residues in freshwater turtle eggshells.