Novel ferrofluid based on water-based deep eutectic solvents: application in dispersive liquid-liquid microextraction of naphthalene-derived plant growth regulators in edible oil

A new ferrofluid extractant (Fe 3 O 4 @SiO 2 -WDES) was ingeniously prepared by coating magnetic Fe 3 O 4 @SiO 2 microspheres with water-based deep eutectic solvent (WDES) and used for dispersive liquid-liquid microextraction (DLLME) and HPLC determination of naphthalene-derived plant growth regulators (PGRs, i.e., 1-naphthylacetic acid, 2-naphthylacetic acid, 1-naphthoxy acetic acid, 2-naphthyloxyacetic acid and 1-naphthylacetamide) in edible oil . Herein, mass transfer of the analytes in DLLME was significantly enhanced via increasing the contact surface by employing the microspheres as the supporter and dispersant of WDES , and phase separation can be efficiently achieved using an external magnet rather than centrifugation in traditional DLLME. Response surface methodology (RSM) based on Box-Behnken design (BBD) was employed for the optimization of core experimental conditions, and Analytical Eco-Scale and Analytical GREEnness Metric Approaches were adopted to evaluate the degree of greenness of the procedure. Under the optimal conditions, satisfactory performances of linearity ranged from 5 to 100 μg/L (R 2 ≥ 0.9982), limit of detection (0.58–0.91 μg/L), limit of quantitation (1.9–3.0 μg/L), precision (RSDs ≤ 5.5%), recovery (81.3%−108.1%) and negligible matrix effect were achieved, which introduced a promising alternative route for the determination of naphthalene-derived plant growth regulators in edible oil.