Ultrasound-Assisted Extraction Combined with Dispersive Liquid-Liquid Microextraction Using Low-Density Solvent—a Novel Approach to Determine Fenvalerate in Strawberry Samples

A new, fast, and environmentally friendly method based on ultrasound-assisted extraction combined with dispersive liquid-liquid microextraction using a low-density solvent was developed and optimized for assessing the levels of fenvalerate in strawberry samples. Variables affecting the performance of both steps were thoroughly investigated. Under the optimum conditions, relative recoveries for strawberry samples were in the range of 88.0–98.0%. The calibration graph was linear in the range of 10–1000 µg/kg, and the limits of detection and quantification were 3 and 10 µg/kg, respectively. The relative standard deviation for 40.0 µg/kg of fenvalerate in strawberry samples was 8.1% (n = 5). The obtained results show that the proposed method is a fast and simple method for the determination of fenvalerate in strawberry samples.