Application of Iron Oxide Magnetic Nanoparticles Modified by Superhydrophobic Cellulose as a Sorbent for Solid‐Phase Extraction of Fat‐Soluble Vitamins

Superhydrophobic cellulose-coated magnetic nanoparticles (SCCMNPs) were synthesized and applied as an advanced solid-phase extraction (SPE) sorbent for the simultaneous extraction of fat-soluble vitamins (FSVs) (A, E and D₃). These modified nanoparticles (NPs) improve extraction efficiency and reduce process time through magnetic separation. The cellulose coating, further modified with stearoyl chloride, enhances sorbent stability and specificity, providing strong hydrophobic interactions while preventing NP aggregation. Extracted vitamins were quantified by high-performance liquid chromatography. Optimization of coating materials revealed that 1.0000 g cellulose and 1.00 mL stearoyl chloride per 1.0000 g magnetic NPs (MNPs) were optimal. The NPs were characterized using Fourier-transform infrared spectroscopy, alternating gradient force magnetometry, dynamic light scattering and zeta potential measurements. Optimized extraction conditions included 50.0 mg sorbent, 10.00 mL sample solution (pH = 5.0), 250 µL tetrahydrofuran as the desorption solvent and 1.5-min sorption/desorption times. Calibration curves exhibited excellent linearity (<i>R</i> ² ≥ 0.999), with a dynamic linear range of 2.4 × 10¹-1.0 × 10³ µg/L, limits of detection ≤8.6 µg/L, repeatability (%relative standard deviation [RSD] ≤ 4.6) and accuracy (recovery ≥79.60%). This is the first report demonstrating the application of stearoyl-modified cellulose in SPE, enabling rapid, solvent-efficient and highly selective vitamin extraction. The method provides a sustainable, cost-effective and high-performance alternative to conventional SPE, achieving efficient recovery with minimal sorbent amount, attributed to its optimized hydrophobicity from the affordable cellulose support. The application of this method in extracting FSVs from pharmaceutical formulations highlights these NPs as a promising next-generation SPE sorbent, offering an efficient, selective and environmentally benign solution.