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