Development of a Sustainable and Practical Natural Deep Eutectic Solvent‐based Ultrasound‐assisted Microextraction Method for Determining Fipronil and Its Degradation Products in Brewed Coffee

Fipronil and its degradation products, such as fipronil sulfide and fipronil desulfinyl, exhibit toxicological concerns and require reliable analytical methods for monitoring in complex matrices such as brewed coffee. This study aimed to develop a novel ultrasound‐assisted liquid–liquid microextraction approach using a natural deep eutectic solvent (NADES), followed by high‐performance liquid chromatography‐diode array detection, for the determination of these compounds in brewed coffee. The optimized extraction parameters obtained through a central composite design consisted of a sample volume of 4.2 mL, 130 µL of NADES as extraction solvent, and an extraction time of 9.2 min. The method was validated, achieving coefficients of determination ( R 2 ) higher than 0.9973 and limits of detection and quantification of 4.5 and 15.0 µg L −1 , respectively, for all analytes. Intraday precision ranged from 6.1% to 13.7%, interday precision from 12.1% to 17.6%, and accuracy (relative recoveries) from 95.8% to 109.3%. The method featured low solvent consumption, reduced waste generation, and high analytical performance, offering a sustainable alternative for monitoring these compounds. High sustainability and practicality were demonstrated by scores of 8.11 and 67.5, obtained using the Sample Preparation Metric of Sustainability and the Blue Applicability Grade Index, respectively. Finally, the method was successfully applied to seven brewed coffee samples purchased in Porto Alegre, Brazil, confirming its applicability as a green workflow in food quality monitoring.