A low-viscosity hydrophobic deep eutectic solvent based ferrofluid for simultaneous vortex-assisted liquid-liquid...

Ferrofluids represent a class of functional materials that combine the flow characteristics of liquids with the magnetic responsiveness of solid magnetic substances. In this study, a novel low-viscosity hydrophobic deep eutectic solvent (HDES) based ferrofluid for vortex-assisted liquid-liquid microextraction (HDES-FF-VA-LLME) technique is proposed for simultaneous extraction of UV filters and parabens from environmental water samples. The ferrofluid was composed of poly(dopamine) modified magnetic nanoparticles and fatty acid based low-viscosity HDESs. The key experimental factors influencing the extraction performance were first screened using a Plackett-Burman design and subsequently optimized through a central composite design. Under the optimized experimental conditions, the method provided limits of detection ranging from 0.05 to 0.25 µg L^-1 and limits of quantification between 0.2 and 1.0 µg L^-1. The intra-day (n = 5) and inter-day (n = 5) relative standard deviations were both below 3.3%, while enrichment factors varied from 22 to 29. Following the extraction process, the ferrofluid phase could be rapidly isolated by applying an external magnetic field, which eliminates the need for conventional phase-separation procedures and significantly reduces separation time. The extraction mechanism was further investigated using density functional theory calculations. Coupled with high-performance liquid chromatography equipped with an ultraviolet detector, the proposed method was successfully applied to the simultaneous determination of UV filters and parabens in environmental water samples, achieving recoveries in the range of 94.4-107.7%. Overall, the developed approach provides a rapid, straightforward, cost-effective, and environmentally friendly microextraction strategy, showing promising potential for applications in environmental monitoring.