Deep eutectic solvent based-ferrofluid ultrasonic-assisted liquid–liquid microextraction for determination of quinolones in milk samples

In the current study, vortex assisted-liquid–liquid microextraction (VA-LLME) pretreatment method was developed based on superparamagnetic nanofluid and deep eutectic solvents for the isolation and preconcentration of quinolones in milk sample. The deep eutectic solvent-ferrofluid (DES-FF) with high extraction ability was prepared by combining DL-menthol/octanoic acid deep eutectic solvent and magnetic nanoparticles, which was mainly related to the strong interactions between extractant and analytes, such as hydrophobic interactions, hydrogen bonding attractions and electrostatic interactions. The functional group, and magnetic characteristics of the synthesized materials were characterized by using Fourier transform-infrared spectroscopy, X-ray diffraction, and vibrating sample magnetometer. The use of vortex instead of dispersed solvent in LLME is simple and quick, reducing the consumption of solvent and shortening the extraction time. The parameters which affected the extraction efficiency were investigated and optimized using response surface methodology (RSM). Under the optimum conditions, linearity (r > 0.996) was in the range of 1.00–100 μg mL−1. Limit of detection (LOD) and quantification (LOQ) of two quinolones varied in 0.30–0.35 μg mL−1 and 0.80–1.0 μg mL−1, respectively. The recoveries were in the range of 84.4–95.4%, RSD of intra-day and inter-day precision were not higher than 5.0% and 7.7%, respectively. Finally, the developed method was successfully applied for the determination of quinolones in milk.