A bio-derived deep eutectic solvent-based ferrofluid for vortex-assisted dispersive micro-solid phase extraction of 2,4-dichlorophenol in water samples.

A hydrophobic deep eutectic solvent (DES)-based ferrofluid was prepared by dispersing oleic acid-coated Fe3O4 nanoparticles into a naturally derived DES composed of menthol and 1-decanol ([Men][Dec]). Comprehensive characterization confirmed the structural and magnetic properties of the resulting [Men][Dec]-Fe3O4-OA ferrofluid. Subsequently, this ferrofluid was coupled with vortex-assisted dispersive micro-solid phase extraction (VA-D-µSPE) for the determination of 2,4-dichlorophenol (2,4-DCP). Under optimized conditions, the method achieved an extraction efficiency of 94.15%. Kinetic and thermodynamic studies were performed to elucidate the extraction behavior, while mechanistic investigations suggested that the enhanced extraction performance resulted from the combined contributions of hydrophobic partitioning and hydrogen-bonding interactions associated with the OA-modified magnetic interface and the DES phase. The ferrofluid exhibited satisfactory reusability, retaining 88% of its initial extraction capacity after six regeneration cycles. The method showed good linearity (R2 = 0.9995) and precision, with intra-day and inter-day relative standard deviations (RSDs) of 0.42% and 0.81%, respectively. The developed method was successfully applied to the determination of 2,4-DCP in real water samples. Furthermore, its environmental greenness was evaluated using AGREEprep and ComplexGAPI, confirming favorable environmental characteristics and potential for sustainable analytical applications. Overall, this work presents a simple, efficient, and eco-friendly ferrofluid-based microextraction strategy for the determination of 2,4-DCP in environmental samples.